The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform

Robert J Delorenzo - One of the best experts on this subject based on the ideXlab platform.

  • In vitro status epilepticus but not spontaneous recurrent seizures cause cell death in Cultured Hippocampal neurons.
    Epilepsy research, 2020
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, Ali Mian, Robert J Delorenzo
    Abstract:

    It is established that the majority but not all of the seizure-induced cell death is associated with status epilepticus while spontaneous recurrent seizures associated with epilepsy do not cause Neuronal death. Extracellular effects and compensatory changes in brain physiology complicate assessment of Neuronal death in vivo as the result of seizures. In this study we utilized a well-characterized in vitro Hippocampal Neuronal Culture model of both continuous high-frequency epileptiform discharges (status epilepticus) and spontaneous recurrent epileptiform discharges (acquired epilepsy) to investigate the direct effects of continuous and episodic electrographic epileptiform discharges on cell death in a carefully controlled extracellular environment. The results from this study indicate that continuous high-frequency epileptiform discharges can cause Neuronal death in a time-dependent manner. Episodic epileptiform seizure activity occurring for the life of the neurons in Culture was not associated with increased Neuronal cell death. Our data confirm observations from clinical and some animal studies that spontaneous recurrent seizures do not initiate cell death. The Hippocampal Neuronal Culture model provides a powerful in vitro tool for carefully evaluating the effects of seizure activity alone on Neuronal viability in the absence of various confounding factors and may provide new insights into the development of novel therapeutic agents to prevent Neuronal injury during status epilepticus.

  • prolonged exposure to win55 212 2 causes downregulation of the cb1 receptor and the development of tolerance to its anticonvulsant effects in the Hippocampal Neuronal Culture model of acquired epilepsy
    Neuropharmacology, 2009
    Co-Authors: Robert E Blair, Laxmikant S Deshpande, Sompong Sombati, Maurice R Elphick, B R Martin, Robert J Delorenzo
    Abstract:

    Abstract Cannabinoids have been shown to cause CB1-receptor-dependent anticonvulsant activity in both in vivo and in vitro models of status epilepticus (SE) and acquired epilepsy (AE). It has been further demonstrated in these models that the endocannabinoid system functions in a tonic manner to suppress seizure discharges through a CB1-receptor-dependent pathway. Although acute cannabinoid treatment has anticonvulsant activity, little is known concerning the effects of prolonged exposure to CB1 agonists and development of tolerance on the epileptic phenotype. This study was carried out to evaluate the effects of prolonged exposure to the CB1 agonist WIN55,212-2 on seizure activity in a Hippocampal Neuronal Culture model of low-Mg2+ induced spontaneous recurrent epileptiform discharges (SREDs). Following low-Mg2+ induced SREDs, Cultures were returned to maintenance media containing 10, 100 or 1000 nM WIN55,212-2 from 4 to 24 h. Whole-cell current-clamp analysis of WIN55,212-2 treated Cultures revealed a concentration-dependent increase in SRED frequency. Immunocytochemical staining revealed that WIN55,212-2 treatment induced a concentration-dependent downregulation of the CB1 receptor in Neuronal processes and at both glutamatergic and GABAergic presynaptic terminals. Prolonged exposure to the inactive enantiomer WIN55,212-3 in low-Mg2+ treated Cultures had no effect on the frequency of SREDs or CB1 receptor staining. The results from this study further substantiate a role for a tonic CB1-receptor-dependent endocannabinoid regulation of seizure discharge and suggest that prolonged exposure to cannabinoids results in the development of tolerance to the anticonvulsant effects of cannabinoids and an exacerbation of seizure activity in the epileptic phenotype.

  • epileptogenesis causes an n methyl d aspartate receptor ca2 dependent decrease in ca2 calmodulin dependent protein kinase ii activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl- d -aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl -2-amino-5-phosphonovaleric acid (APV) 25 µM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • The novel antiepileptic drug carisbamate (RWJ 333369) is effective in inhibiting spontaneous recurrent seizure discharges and blocking sustained repetitive firing in Cultured Hippocampal neurons
    Epilepsy Research, 2008
    Co-Authors: Laxmikant S Deshpande, Sompong Sombati, Nisha Nagarkatti, Robert J Delorenzo
    Abstract:

    Summary This study was initiated to investigate effects of the novel neuromodulator carisbamate (RWJ 333369) in the Hippocampal Neuronal Culture model of status epilepticus and spontaneous epileptiform discharges. Whole-cell current clamp techniques were used to determine the effects of carisbamate on spontaneous recurrent epileptiform discharges (SREDs, in vitro epilepsy), depolarization-induced sustained repetitive firing (SRF) and low Mg 2+ -induced continuous high frequency spiking (in vitro status epilepticus). This in vitro model is an important tool to study the effects of anticonvulsant drugs (AEDs) on SREDs that occur for the life of the neurons in Culture. Carisbamate dose dependently blocked the expression and reoccurrence of SREDs. The ED 50 value for its antiepileptic effect was 58.75±2.43μM. Inhibition of SRF is considered a common attribute of many AEDs. Carisbamate (100μM) significantly decreased SRF in Hippocampal neurons. All these effects of carisbamate were reversed during a 5 to 30min drug washout period. When exposed to low Mg 2+ medium Cultured Hippocampal neurons exhibit high frequency spiking. This form of in vitro status epilepticus is not effectively blocked by conventional AEDs that are known to be effective in treating status epilepticus in humans. Carisbamate, like phenytoin and phenobarbital, had little or no effect on low Mg 2+ -induced continuous high frequency spiking. These results characterize the effects of carisbamate in the Hippocampal Neuronal Culture model of epileptiform discharges and suggest that the ability of carisbamate to inhibit depolarization-induced SRF may account in part for some of it's anticonvulsant effect.

  • Epileptogenesis causes an N-methyl-d-aspartate receptor/Ca2+-dependent decrease in Ca2+/calmodulin-dependent protein kinase II activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges.
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl-d-aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl-2-amino-5-phosphonovaleric acid (APV) 25 microM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

Robert E Blair - One of the best experts on this subject based on the ideXlab platform.

  • In vitro status epilepticus but not spontaneous recurrent seizures cause cell death in Cultured Hippocampal neurons.
    Epilepsy research, 2020
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, Ali Mian, Robert J Delorenzo
    Abstract:

    It is established that the majority but not all of the seizure-induced cell death is associated with status epilepticus while spontaneous recurrent seizures associated with epilepsy do not cause Neuronal death. Extracellular effects and compensatory changes in brain physiology complicate assessment of Neuronal death in vivo as the result of seizures. In this study we utilized a well-characterized in vitro Hippocampal Neuronal Culture model of both continuous high-frequency epileptiform discharges (status epilepticus) and spontaneous recurrent epileptiform discharges (acquired epilepsy) to investigate the direct effects of continuous and episodic electrographic epileptiform discharges on cell death in a carefully controlled extracellular environment. The results from this study indicate that continuous high-frequency epileptiform discharges can cause Neuronal death in a time-dependent manner. Episodic epileptiform seizure activity occurring for the life of the neurons in Culture was not associated with increased Neuronal cell death. Our data confirm observations from clinical and some animal studies that spontaneous recurrent seizures do not initiate cell death. The Hippocampal Neuronal Culture model provides a powerful in vitro tool for carefully evaluating the effects of seizure activity alone on Neuronal viability in the absence of various confounding factors and may provide new insights into the development of novel therapeutic agents to prevent Neuronal injury during status epilepticus.

  • prolonged exposure to win55 212 2 causes downregulation of the cb1 receptor and the development of tolerance to its anticonvulsant effects in the Hippocampal Neuronal Culture model of acquired epilepsy
    Neuropharmacology, 2009
    Co-Authors: Robert E Blair, Laxmikant S Deshpande, Sompong Sombati, Maurice R Elphick, B R Martin, Robert J Delorenzo
    Abstract:

    Abstract Cannabinoids have been shown to cause CB1-receptor-dependent anticonvulsant activity in both in vivo and in vitro models of status epilepticus (SE) and acquired epilepsy (AE). It has been further demonstrated in these models that the endocannabinoid system functions in a tonic manner to suppress seizure discharges through a CB1-receptor-dependent pathway. Although acute cannabinoid treatment has anticonvulsant activity, little is known concerning the effects of prolonged exposure to CB1 agonists and development of tolerance on the epileptic phenotype. This study was carried out to evaluate the effects of prolonged exposure to the CB1 agonist WIN55,212-2 on seizure activity in a Hippocampal Neuronal Culture model of low-Mg2+ induced spontaneous recurrent epileptiform discharges (SREDs). Following low-Mg2+ induced SREDs, Cultures were returned to maintenance media containing 10, 100 or 1000 nM WIN55,212-2 from 4 to 24 h. Whole-cell current-clamp analysis of WIN55,212-2 treated Cultures revealed a concentration-dependent increase in SRED frequency. Immunocytochemical staining revealed that WIN55,212-2 treatment induced a concentration-dependent downregulation of the CB1 receptor in Neuronal processes and at both glutamatergic and GABAergic presynaptic terminals. Prolonged exposure to the inactive enantiomer WIN55,212-3 in low-Mg2+ treated Cultures had no effect on the frequency of SREDs or CB1 receptor staining. The results from this study further substantiate a role for a tonic CB1-receptor-dependent endocannabinoid regulation of seizure discharge and suggest that prolonged exposure to cannabinoids results in the development of tolerance to the anticonvulsant effects of cannabinoids and an exacerbation of seizure activity in the epileptic phenotype.

  • epileptogenesis causes an n methyl d aspartate receptor ca2 dependent decrease in ca2 calmodulin dependent protein kinase ii activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl- d -aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl -2-amino-5-phosphonovaleric acid (APV) 25 µM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • Epileptogenesis causes an N-methyl-d-aspartate receptor/Ca2+-dependent decrease in Ca2+/calmodulin-dependent protein kinase II activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges.
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl-d-aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl-2-amino-5-phosphonovaleric acid (APV) 25 microM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • development of pharmacoresistance to benzodiazepines but not cannabinoids in the Hippocampal Neuronal Culture model of status epilepticus
    Experimental Neurology, 2007
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, B R Martin, Nisha Nagarkatti, Robert J Delorenzo
    Abstract:

    Abstract Status epilepticus (SE) is a life-threatening neurological disorder associated with a significant morbidity and mortality. Benzodiazepines are the initial drugs of choice for the treatment of SE. Despite aggressive treatment, over 40% of SE cases are refractory to the initial treatment with two or more medications. It would be a major advance in the clinical management of SE to identify novel anticonvulsant agents that do not lose their ability to treat SE with increasing seizure duration. Cannabinoids have recently been demonstrated to regulate seizure activity in brain. However, it remains to be seen whether they develop pharmacoresistance upon prolonged SE. In this study, we used low Mg2+ to induce SE in Hippocampal Neuronal Cultures and in agreement with animal models and human SE confirm the development of resistance to benzodiazepine with increasing durations of SE. Thus, lorazepam (1 μM) was effective in blocking low Mg2+ induced high-frequency spiking for up to 30 min into SE. However, by 1 h and 2 h of SE onset it was only 10–15% effective in suppressing SE. In contrast, the cannabinoid type-1 (CB1) receptor agonist, WIN 55,212-2 (1 μM) in a CB1 receptor-dependent manner completely abolished SE at all the time points tested even out to 2 h after SE onset, a condition where resistance developed to lorazepam. Thus, the use of cannabinoids in the treatment of SE may offer a unique approach to controlling SE without the development of pharmacoresistance observed with conventional treatments.

Sompong Sombati - One of the best experts on this subject based on the ideXlab platform.

  • In vitro status epilepticus but not spontaneous recurrent seizures cause cell death in Cultured Hippocampal neurons.
    Epilepsy research, 2020
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, Ali Mian, Robert J Delorenzo
    Abstract:

    It is established that the majority but not all of the seizure-induced cell death is associated with status epilepticus while spontaneous recurrent seizures associated with epilepsy do not cause Neuronal death. Extracellular effects and compensatory changes in brain physiology complicate assessment of Neuronal death in vivo as the result of seizures. In this study we utilized a well-characterized in vitro Hippocampal Neuronal Culture model of both continuous high-frequency epileptiform discharges (status epilepticus) and spontaneous recurrent epileptiform discharges (acquired epilepsy) to investigate the direct effects of continuous and episodic electrographic epileptiform discharges on cell death in a carefully controlled extracellular environment. The results from this study indicate that continuous high-frequency epileptiform discharges can cause Neuronal death in a time-dependent manner. Episodic epileptiform seizure activity occurring for the life of the neurons in Culture was not associated with increased Neuronal cell death. Our data confirm observations from clinical and some animal studies that spontaneous recurrent seizures do not initiate cell death. The Hippocampal Neuronal Culture model provides a powerful in vitro tool for carefully evaluating the effects of seizure activity alone on Neuronal viability in the absence of various confounding factors and may provide new insights into the development of novel therapeutic agents to prevent Neuronal injury during status epilepticus.

  • prolonged exposure to win55 212 2 causes downregulation of the cb1 receptor and the development of tolerance to its anticonvulsant effects in the Hippocampal Neuronal Culture model of acquired epilepsy
    Neuropharmacology, 2009
    Co-Authors: Robert E Blair, Laxmikant S Deshpande, Sompong Sombati, Maurice R Elphick, B R Martin, Robert J Delorenzo
    Abstract:

    Abstract Cannabinoids have been shown to cause CB1-receptor-dependent anticonvulsant activity in both in vivo and in vitro models of status epilepticus (SE) and acquired epilepsy (AE). It has been further demonstrated in these models that the endocannabinoid system functions in a tonic manner to suppress seizure discharges through a CB1-receptor-dependent pathway. Although acute cannabinoid treatment has anticonvulsant activity, little is known concerning the effects of prolonged exposure to CB1 agonists and development of tolerance on the epileptic phenotype. This study was carried out to evaluate the effects of prolonged exposure to the CB1 agonist WIN55,212-2 on seizure activity in a Hippocampal Neuronal Culture model of low-Mg2+ induced spontaneous recurrent epileptiform discharges (SREDs). Following low-Mg2+ induced SREDs, Cultures were returned to maintenance media containing 10, 100 or 1000 nM WIN55,212-2 from 4 to 24 h. Whole-cell current-clamp analysis of WIN55,212-2 treated Cultures revealed a concentration-dependent increase in SRED frequency. Immunocytochemical staining revealed that WIN55,212-2 treatment induced a concentration-dependent downregulation of the CB1 receptor in Neuronal processes and at both glutamatergic and GABAergic presynaptic terminals. Prolonged exposure to the inactive enantiomer WIN55,212-3 in low-Mg2+ treated Cultures had no effect on the frequency of SREDs or CB1 receptor staining. The results from this study further substantiate a role for a tonic CB1-receptor-dependent endocannabinoid regulation of seizure discharge and suggest that prolonged exposure to cannabinoids results in the development of tolerance to the anticonvulsant effects of cannabinoids and an exacerbation of seizure activity in the epileptic phenotype.

  • epileptogenesis causes an n methyl d aspartate receptor ca2 dependent decrease in ca2 calmodulin dependent protein kinase ii activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl- d -aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl -2-amino-5-phosphonovaleric acid (APV) 25 µM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • The novel antiepileptic drug carisbamate (RWJ 333369) is effective in inhibiting spontaneous recurrent seizure discharges and blocking sustained repetitive firing in Cultured Hippocampal neurons
    Epilepsy Research, 2008
    Co-Authors: Laxmikant S Deshpande, Sompong Sombati, Nisha Nagarkatti, Robert J Delorenzo
    Abstract:

    Summary This study was initiated to investigate effects of the novel neuromodulator carisbamate (RWJ 333369) in the Hippocampal Neuronal Culture model of status epilepticus and spontaneous epileptiform discharges. Whole-cell current clamp techniques were used to determine the effects of carisbamate on spontaneous recurrent epileptiform discharges (SREDs, in vitro epilepsy), depolarization-induced sustained repetitive firing (SRF) and low Mg 2+ -induced continuous high frequency spiking (in vitro status epilepticus). This in vitro model is an important tool to study the effects of anticonvulsant drugs (AEDs) on SREDs that occur for the life of the neurons in Culture. Carisbamate dose dependently blocked the expression and reoccurrence of SREDs. The ED 50 value for its antiepileptic effect was 58.75±2.43μM. Inhibition of SRF is considered a common attribute of many AEDs. Carisbamate (100μM) significantly decreased SRF in Hippocampal neurons. All these effects of carisbamate were reversed during a 5 to 30min drug washout period. When exposed to low Mg 2+ medium Cultured Hippocampal neurons exhibit high frequency spiking. This form of in vitro status epilepticus is not effectively blocked by conventional AEDs that are known to be effective in treating status epilepticus in humans. Carisbamate, like phenytoin and phenobarbital, had little or no effect on low Mg 2+ -induced continuous high frequency spiking. These results characterize the effects of carisbamate in the Hippocampal Neuronal Culture model of epileptiform discharges and suggest that the ability of carisbamate to inhibit depolarization-induced SRF may account in part for some of it's anticonvulsant effect.

  • Epileptogenesis causes an N-methyl-d-aspartate receptor/Ca2+-dependent decrease in Ca2+/calmodulin-dependent protein kinase II activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges.
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl-d-aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl-2-amino-5-phosphonovaleric acid (APV) 25 microM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

Severn B Churn - One of the best experts on this subject based on the ideXlab platform.

  • epileptogenesis causes an n methyl d aspartate receptor ca2 dependent decrease in ca2 calmodulin dependent protein kinase ii activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl- d -aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl -2-amino-5-phosphonovaleric acid (APV) 25 µM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • Epileptogenesis causes an N-methyl-d-aspartate receptor/Ca2+-dependent decrease in Ca2+/calmodulin-dependent protein kinase II activity in a Hippocampal Neuronal Culture model of spontaneous recurrent epileptiform discharges.
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the Hippocampal Neuronal Culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in Hippocampal Cultures involves a Ca2+/N-methyl-d-aspartate (NMDA) receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl-2-amino-5-phosphonovaleric acid (APV) 25 microM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • long lasting decrease in Neuronal ca2 calmodulin dependent protein kinase ii activity in a Hippocampal Neuronal Culture model of spontaneous recurrent seizures
    Brain Research, 1999
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Ca2+/calmodulin-dependent protein kinase II (CaM Kinase II) activity was evaluated in a well-characterized in vitro model of epileptiform activity. Long-lasting spontaneous recurrent seizure (SRS) activity was induced in Hippocampal Neuronal Cultures by exposure to low Mg2+ media for 3 h. Analysis of endogenous Ca2+/calmodulin-dependent phosphorylation revealed a significant long-lasting decrease in 32 P incorporation into the α (50 kDa) and β (60 kDa) subunits of CaM kinase II in association with the induction of SRS activity in this preparation. Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptides, Autocamtide-2 and Syntide II, was also significantly reduced following the induction of SRSs and persisted for the life of the neurons in Culture. The decrement in CaM kinase II activity associated with low Mg2+ treatment remained significantly decreased when values were corrected for changes in levels of α subunit immunoreactivity and Neuronal cell loss. Addition of the protein phosphatase inhibitors, okadaic acid and cyclosporin A, to the phosphorylation reaction did not block the SRS-associated decrease in substrate phosphorylation, indicating that enhanced phosphatase activity was not a contributing factor to the observed decrease in phosphate incorporation. The findings of this study demonstrate that CaM kinase II activity is decreased in association with epileptogenesis observed in these Hippocampal Cultures and may contribute to the production and maintenance of SRSs in this model.

  • Long-lasting decrease in Neuronal Ca2+/calmodulin-dependent protein kinase II activity in a Hippocampal Neuronal Culture model of spontaneous recurrent seizures.
    Brain research, 1999
    Co-Authors: R E Blair, Severn B Churn, S Sombati, R J Delorenzo
    Abstract:

    Ca2+/calmodulin-dependent protein kinase II (CaM Kinase II) activity was evaluated in a well-characterized in vitro model of epileptiform activity. Long-lasting spontaneous recurrent seizure (SRS) activity was induced in Hippocampal Neuronal Cultures by exposure to low Mg2+ media for 3 h. Analysis of endogenous Ca2+/calmodulin-dependent phosphorylation revealed a significant long-lasting decrease in 32P incorporation into the alpha (50 kDa) and beta (60 kDa) subunits of CaM kinase II in association with the induction of SRS activity in this preparation. Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptides, Autocamtide-2 and Syntide II, was also significantly reduced following the induction of SRSs and persisted for the life of the neurons in Culture. The decrement in CaM kinase II activity associated with low Mg2+ treatment remained significantly decreased when values were corrected for changes in levels of alpha subunit immunoreactivity and Neuronal cell loss. Addition of the protein phosphatase inhibitors, okadaic acid and cyclosporin A, to the phosphorylation reaction did not block the SRS-associated decrease in substrate phosphorylation, indicating that enhanced phosphatase activity was not a contributing factor to the observed decrease in phosphate incorporation. The findings of this study demonstrate that CaM kinase II activity is decreased in association with epileptogenesis observed in these Hippocampal Cultures and may contribute to the production and maintenance of SRSs in this model.

  • Long-lasting decrease in Neuronal Ca2+/calmodulin-dependent protein kinase II activity in a Hippocampal Neuronal Culture model of spontaneous recurrent seizures.
    Brain Research, 1999
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Ca2+/calmodulin-dependent protein kinase II (CaM Kinase II) activity was evaluated in a well-characterized in vitro model of epileptiform activity. Long-lasting spontaneous recurrent seizure (SRS) activity was induced in Hippocampal Neuronal Cultures by exposure to low Mg2+ media for 3 h. Analysis of endogenous Ca2+/calmodulin-dependent phosphorylation revealed a significant long-lasting decrease in 32 P incorporation into the α (50 kDa) and β (60 kDa) subunits of CaM kinase II in association with the induction of SRS activity in this preparation. Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptides, Autocamtide-2 and Syntide II, was also significantly reduced following the induction of SRSs and persisted for the life of the neurons in Culture. The decrement in CaM kinase II activity associated with low Mg2+ treatment remained significantly decreased when values were corrected for changes in levels of α subunit immunoreactivity and Neuronal cell loss. Addition of the protein phosphatase inhibitors, okadaic acid and cyclosporin A, to the phosphorylation reaction did not block the SRS-associated decrease in substrate phosphorylation, indicating that enhanced phosphatase activity was not a contributing factor to the observed decrease in phosphate incorporation. The findings of this study demonstrate that CaM kinase II activity is decreased in association with epileptogenesis observed in these Hippocampal Cultures and may contribute to the production and maintenance of SRSs in this model.

Laxmikant S Deshpande - One of the best experts on this subject based on the ideXlab platform.

  • In vitro status epilepticus but not spontaneous recurrent seizures cause cell death in Cultured Hippocampal neurons.
    Epilepsy research, 2020
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, Ali Mian, Robert J Delorenzo
    Abstract:

    It is established that the majority but not all of the seizure-induced cell death is associated with status epilepticus while spontaneous recurrent seizures associated with epilepsy do not cause Neuronal death. Extracellular effects and compensatory changes in brain physiology complicate assessment of Neuronal death in vivo as the result of seizures. In this study we utilized a well-characterized in vitro Hippocampal Neuronal Culture model of both continuous high-frequency epileptiform discharges (status epilepticus) and spontaneous recurrent epileptiform discharges (acquired epilepsy) to investigate the direct effects of continuous and episodic electrographic epileptiform discharges on cell death in a carefully controlled extracellular environment. The results from this study indicate that continuous high-frequency epileptiform discharges can cause Neuronal death in a time-dependent manner. Episodic epileptiform seizure activity occurring for the life of the neurons in Culture was not associated with increased Neuronal cell death. Our data confirm observations from clinical and some animal studies that spontaneous recurrent seizures do not initiate cell death. The Hippocampal Neuronal Culture model provides a powerful in vitro tool for carefully evaluating the effects of seizure activity alone on Neuronal viability in the absence of various confounding factors and may provide new insights into the development of novel therapeutic agents to prevent Neuronal injury during status epilepticus.

  • prolonged exposure to win55 212 2 causes downregulation of the cb1 receptor and the development of tolerance to its anticonvulsant effects in the Hippocampal Neuronal Culture model of acquired epilepsy
    Neuropharmacology, 2009
    Co-Authors: Robert E Blair, Laxmikant S Deshpande, Sompong Sombati, Maurice R Elphick, B R Martin, Robert J Delorenzo
    Abstract:

    Abstract Cannabinoids have been shown to cause CB1-receptor-dependent anticonvulsant activity in both in vivo and in vitro models of status epilepticus (SE) and acquired epilepsy (AE). It has been further demonstrated in these models that the endocannabinoid system functions in a tonic manner to suppress seizure discharges through a CB1-receptor-dependent pathway. Although acute cannabinoid treatment has anticonvulsant activity, little is known concerning the effects of prolonged exposure to CB1 agonists and development of tolerance on the epileptic phenotype. This study was carried out to evaluate the effects of prolonged exposure to the CB1 agonist WIN55,212-2 on seizure activity in a Hippocampal Neuronal Culture model of low-Mg2+ induced spontaneous recurrent epileptiform discharges (SREDs). Following low-Mg2+ induced SREDs, Cultures were returned to maintenance media containing 10, 100 or 1000 nM WIN55,212-2 from 4 to 24 h. Whole-cell current-clamp analysis of WIN55,212-2 treated Cultures revealed a concentration-dependent increase in SRED frequency. Immunocytochemical staining revealed that WIN55,212-2 treatment induced a concentration-dependent downregulation of the CB1 receptor in Neuronal processes and at both glutamatergic and GABAergic presynaptic terminals. Prolonged exposure to the inactive enantiomer WIN55,212-3 in low-Mg2+ treated Cultures had no effect on the frequency of SREDs or CB1 receptor staining. The results from this study further substantiate a role for a tonic CB1-receptor-dependent endocannabinoid regulation of seizure discharge and suggest that prolonged exposure to cannabinoids results in the development of tolerance to the anticonvulsant effects of cannabinoids and an exacerbation of seizure activity in the epileptic phenotype.

  • The novel antiepileptic drug carisbamate (RWJ 333369) is effective in inhibiting spontaneous recurrent seizure discharges and blocking sustained repetitive firing in Cultured Hippocampal neurons
    Epilepsy Research, 2008
    Co-Authors: Laxmikant S Deshpande, Sompong Sombati, Nisha Nagarkatti, Robert J Delorenzo
    Abstract:

    Summary This study was initiated to investigate effects of the novel neuromodulator carisbamate (RWJ 333369) in the Hippocampal Neuronal Culture model of status epilepticus and spontaneous epileptiform discharges. Whole-cell current clamp techniques were used to determine the effects of carisbamate on spontaneous recurrent epileptiform discharges (SREDs, in vitro epilepsy), depolarization-induced sustained repetitive firing (SRF) and low Mg 2+ -induced continuous high frequency spiking (in vitro status epilepticus). This in vitro model is an important tool to study the effects of anticonvulsant drugs (AEDs) on SREDs that occur for the life of the neurons in Culture. Carisbamate dose dependently blocked the expression and reoccurrence of SREDs. The ED 50 value for its antiepileptic effect was 58.75±2.43μM. Inhibition of SRF is considered a common attribute of many AEDs. Carisbamate (100μM) significantly decreased SRF in Hippocampal neurons. All these effects of carisbamate were reversed during a 5 to 30min drug washout period. When exposed to low Mg 2+ medium Cultured Hippocampal neurons exhibit high frequency spiking. This form of in vitro status epilepticus is not effectively blocked by conventional AEDs that are known to be effective in treating status epilepticus in humans. Carisbamate, like phenytoin and phenobarbital, had little or no effect on low Mg 2+ -induced continuous high frequency spiking. These results characterize the effects of carisbamate in the Hippocampal Neuronal Culture model of epileptiform discharges and suggest that the ability of carisbamate to inhibit depolarization-induced SRF may account in part for some of it's anticonvulsant effect.

  • development of pharmacoresistance to benzodiazepines but not cannabinoids in the Hippocampal Neuronal Culture model of status epilepticus
    Experimental Neurology, 2007
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, B R Martin, Nisha Nagarkatti, Robert J Delorenzo
    Abstract:

    Abstract Status epilepticus (SE) is a life-threatening neurological disorder associated with a significant morbidity and mortality. Benzodiazepines are the initial drugs of choice for the treatment of SE. Despite aggressive treatment, over 40% of SE cases are refractory to the initial treatment with two or more medications. It would be a major advance in the clinical management of SE to identify novel anticonvulsant agents that do not lose their ability to treat SE with increasing seizure duration. Cannabinoids have recently been demonstrated to regulate seizure activity in brain. However, it remains to be seen whether they develop pharmacoresistance upon prolonged SE. In this study, we used low Mg2+ to induce SE in Hippocampal Neuronal Cultures and in agreement with animal models and human SE confirm the development of resistance to benzodiazepine with increasing durations of SE. Thus, lorazepam (1 μM) was effective in blocking low Mg2+ induced high-frequency spiking for up to 30 min into SE. However, by 1 h and 2 h of SE onset it was only 10–15% effective in suppressing SE. In contrast, the cannabinoid type-1 (CB1) receptor agonist, WIN 55,212-2 (1 μM) in a CB1 receptor-dependent manner completely abolished SE at all the time points tested even out to 2 h after SE onset, a condition where resistance developed to lorazepam. Thus, the use of cannabinoids in the treatment of SE may offer a unique approach to controlling SE without the development of pharmacoresistance observed with conventional treatments.

  • Endocannabinoids block status epilepticus in Cultured Hippocampal neurons
    European Journal of Pharmacology, 2007
    Co-Authors: Laxmikant S Deshpande, Robert E Blair, Sompong Sombati, Billy R Martin, Julie M. Ziobro, Robert J Delorenzo
    Abstract:

    Status epilepticus is a serious neurological disorder associated with a significant morbidity and mortality. Antiepileptic drugs such as diazepam, phenobarbital and phenytoin are the mainstay of status epilepticus treatment. However, over 20% of status epilepticus cases are refractory to the initial treatment with two or more antiepileptic drugs. Endocannabinoids have been implicated as playing an important role in regulating seizure activity and seizure termination. This study evaluated the effects of the major endocannabinoids methanandamide and 2-arachidonylglycerol (2-AG) on status epilepticus in the low-Mg(2+) Hippocampal Neuronal Culture model. Status epilepticus in this model was resistant to treatment with phenobarbital and phenytoin. Methanandamide and 2-AG inhibited status epilepticus in a dose-dependent manner with an EC(50) of 145+/-4.15 nM and 1.68+/-0.19 microM, respectively. In addition, the anti-status epilepticus effects of methanandamide and 2-AG were mediated by activation of the cannabinoid CB(1) receptor since they were blocked by the cannabinoid CB(1) receptor antagonist AM251. These results provide the first evidence that the endocannabinoids, methanandamide and 2-AG, are effective inhibitors of refractory status epilepticus in the Hippocampal Neuronal Culture model and indicate that regulating the endocannabinoid system may provide a novel therapeutic approach for treating refractory status epilepticus.