The Experts below are selected from a list of 105 Experts worldwide ranked by ideXlab platform
H E Scharfman - One of the best experts on this subject based on the ideXlab platform.
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hyperexcitability of entorhinal cortex and hippocampus after application of aminooxyacetic acid aoaa to layer iii of the rat medial entorhinal cortex in vitro
Journal of Neurophysiology, 1996Co-Authors: H E ScharfmanAbstract:1. Injection of aminooxyacetic acid (AOAA) into the entorhinal cortex in vivo produces acute seizures and cell loss in medial entorhinal cortex. To understand these effects, AOAA was applied directly to the medial entorhinal cortex in slices containing both the entorhinal cortex and hippocampus. Extracellular and intracellular recordings were made in both the entorhinal cortex and hippocampus to study responses to Angular Bundle stimulation and spontaneous activity. 2. AOAA was applied focally by leak from a micropipette or by pressure ejection. Evoked potentials increased gradually within 5 min of application, particularly the late, negative components. Evoked potentials continued to increase for up to 1 h, and these changes persisted for the remainder of the experiment (up to 5 h after drug application). 3. Paired pulse facilitation (100-ms interval) was also enhanced after AOAA application. Increasing stimulus frequency to 1-10 Hz increased evoked potentials further, and after several seconds of such s...
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hyperexcitability of entorhinal cortex and hippocampus after application of aminooxyacetic acid aoaa to layer iii of the rat medial entorhinal cortex in vitro
Journal of Neurophysiology, 1996Co-Authors: H E ScharfmanAbstract:1. Injection of aminooxyacetic acid (AOAA) into the entorhinal cortex in vivo produces acute seizures and cell loss in medial entorhinal cortex. To understand these effects, AOAA was applied directly to the medial entorhinal cortex in slices containing both the entorhinal cortex and hippocampus. Extracellular and intracellular recordings were made in both the entorhinal cortex and hippocampus to study responses to Angular Bundle stimulation and spontaneous activity. 2. AOAA was applied focally by leak from a micropipette or by pressure ejection. Evoked potentials increased gradually within 5 min of application, particularly the late, negative components. Evoked potentials continued to increase for up to 1 h, and these changes persisted for the remainder of the experiment (up to 5 h after drug application). 3. Paired pulse facilitation (100-ms interval) was also enhanced after AOAA application. Increasing stimulus frequency to 1-10 Hz increased evoked potentials further, and after several seconds of such s...
Joe E Springer - One of the best experts on this subject based on the ideXlab platform.
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neurotrophic factor mrna expression in dentate gyrus is increased following Angular Bundle transection
Brain Research, 1994Co-Authors: Byoung Joo Gwag, Francis M Sessler, Kelly Kimmerer, Joe E SpringerAbstract:Abstract In the central nervous system, the highest levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA are found in the hippocampal formation. In the present study, we report that a unilateral transection of the Angular Bundle, which relays cortical information via the entorhinal cortex to the hippocampal formation, increases NGF and BDNF mRNA in the ipsilateral dentate gyrus. Within 4 hours following transection, the hybridization signal for NGF and BDNF mRNA increases in stratum granulosum 3- and 5-fold, respectively, compared to control levels. This lesion-induced increase of both mRNA returns to control levels within 24 hours and is maintained for at least 5 days. The induction is not prevented by pretreatment with AP-5, CNQX, or cholinergic denervation due to transection of the fimbria-fornix. Finally, the induction of neurotrophin mRNA is preceded by an increase in c- fos mRNA. These results provide evidence that transection of the cortical input to the hippocampal formation upregulates NGF and BNDF mRNA selectively in stratum granulosum. We suggest that the increased expression of NGF and BDNF mRNA may be an early step in the synaptic rearrangement of neurotrophin responsive cholinergic afferents observed following damage to the entorhinal cortex.
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neurotrophic factor mrna expression in dentate gyrus is increased following in vivo stimulation of the Angular Bundle
Molecular Brain Research, 1994Co-Authors: Joe E Springer, Byoung Joo Gwag, Francis M SesslerAbstract:Abstract Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two structurally-related neurotrophins synthesized in dentate gyrus granule cells and pyramidal neurons of the hippocampal formation. These neurons receive excitatory glutamatergic afferents from the entorhinal cortex via the Angular Bundle/perforant path. In the present study, we tested whether electrophysiological stimulation of this glutamatergic pathway modifies NGF or BDNF messenger RNA (mRNA) expression in vivo. Within hours following brief trains of high frequency Angular Bundle stimulation, the levels of mRNA encoding both neurotrophins were increased exclusively in granule cells of the ipsilateral dentate gyrus. The increase in neurotrophic factor mRNA expression was found to be mediated through the N- methyl- d -aspartate (NMDA) glutamate receptor subtype, and occurred in the absence of seizure. These findings provide evidence that neurotrophic factor mRNA levels in the hippocampal formation are increased by direct activation of excitatory afferents originating in the entorhinal cortex. We suggest that the function of some neurotrophin-responsive neuronal populations may depend upon the integrity and activity of neurons in the entorhinal cortex, a population of neurons reported to be compromised in patients with Alzheimer's disease.
Raymond P Kesner - One of the best experts on this subject based on the ideXlab platform.
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disruption of the direct perforant path input to the ca1 subregion of the dorsal hippocampus interferes with spatial working memory and novelty detection
Behavioural Brain Research, 2008Co-Authors: David R Vago, Raymond P KesnerAbstract:Subregional analyses of the hippocampus suggest CA1-dependent memory processes rely heavily upon interactions between the CA1 subregion and entorhinal cortex. There is evidence that the direct perforant path (pp) projection to CA1 is selectively modulated by dopamine while having little to no effect on the Schaffer collateral (SC) projection to CA1. The current study takes advantage of this pharmacological dissociation to demonstrate that local infusion of the non-selective dopamine agonist, apomorphine (10, 15 µg), into the CA1 subregion of awake animals produces impairments in working memory at intermediate (5 min), but not short-term (10 sec) delays within a delayed nonmatch-to-place task on a radial arm maze. Sustained impairments were also found in a novel context with similar object-space relationships. Infusion of apomorphine into CA1 is also shown here to produce deficits in spatial, but not non-spatial novelty detection within an object exploration paradigm. In contrast, apomorphine produces no behavioral deficits when infused into the CA3 subregion or overlying cortex. These behavioral studies are supported by previous electrophysiological data that demonstrate local infusion of the same doses of apomorphine significantly modifies evoked responses in the distal dendrites of CA1 following Angular Bundle stimulation, but produces no significant effects in the proximal dendritic layer following stimulation of the SC. These results support a modulatory role for dopamine in EC-CA1, but not CA3-CA1 circuitry, and suggest the possibility of a fundamental role for EC-CA1 synaptic transmission in terms of detection of spatial novelty, and intermediate-term, but not short-term spatial working memory or object-novelty detection.
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the role of the direct perforant path input to the ca1 subregion of the dorsal hippocampus in memory retention and retrieval
Hippocampus, 2007Co-Authors: David R Vago, Adam K Bevan, Raymond P KesnerAbstract:Subregional analyses of the hippocampus have suggested a selective role for the CA1 subregion in intermediate/long-term spatial memory and consolidation, but not short-term acquisition or encoding processes. It remains unclear how the direct cortical projection to CA1 via the perforant path (pp) contributes to these CA1-dependent processes. It has been suggested that dopamine selectively modulates the pp projection to CA1 while having little to no effect on the Schaffer collateral (SC) projection to CA1. This series of behavioral and electrophysiological experiments takes advantage of this pharmacological dissociation to demonstrate that the direct pp inputs to CA1 are critical in CA1-dependent intermediate-term retention and retrieval function. Here we demonstrate that local infusion of the nonselective dopamine agonist, apomorphine (10, 15 microg), into the CA1 subregion of awake animals produces impairments in between-day retention and retrieval, sparing within-day encoding of a modified Hebb-Williams maze and contextual conditioning of fear. In contrast, apomorphine produces no deficits when infused into the CA3 subregion. To complement the behavioral analyses, electrophysiological data was collected. In anesthetized animals, local infusion of the same doses of apomorphine significantly modifies evoked responses in the distal dendrites of CA1 following Angular Bundle stimulation, but produces no significant effects in the more proximal dendritic layer following stimulation of the SC. These results support a modulatory role for dopamine in the EC-CA1, but not CA3-CA1 circuitry, and suggest the possibility of a more fundamental role for EC-CA1 synaptic transmission in terms of intermediate-term, but not short-term spatial memory.
Byoung Joo Gwag - One of the best experts on this subject based on the ideXlab platform.
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neurotrophic factor mrna expression in dentate gyrus is increased following Angular Bundle transection
Brain Research, 1994Co-Authors: Byoung Joo Gwag, Francis M Sessler, Kelly Kimmerer, Joe E SpringerAbstract:Abstract In the central nervous system, the highest levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA are found in the hippocampal formation. In the present study, we report that a unilateral transection of the Angular Bundle, which relays cortical information via the entorhinal cortex to the hippocampal formation, increases NGF and BDNF mRNA in the ipsilateral dentate gyrus. Within 4 hours following transection, the hybridization signal for NGF and BDNF mRNA increases in stratum granulosum 3- and 5-fold, respectively, compared to control levels. This lesion-induced increase of both mRNA returns to control levels within 24 hours and is maintained for at least 5 days. The induction is not prevented by pretreatment with AP-5, CNQX, or cholinergic denervation due to transection of the fimbria-fornix. Finally, the induction of neurotrophin mRNA is preceded by an increase in c- fos mRNA. These results provide evidence that transection of the cortical input to the hippocampal formation upregulates NGF and BNDF mRNA selectively in stratum granulosum. We suggest that the increased expression of NGF and BDNF mRNA may be an early step in the synaptic rearrangement of neurotrophin responsive cholinergic afferents observed following damage to the entorhinal cortex.
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neurotrophic factor mrna expression in dentate gyrus is increased following in vivo stimulation of the Angular Bundle
Molecular Brain Research, 1994Co-Authors: Joe E Springer, Byoung Joo Gwag, Francis M SesslerAbstract:Abstract Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two structurally-related neurotrophins synthesized in dentate gyrus granule cells and pyramidal neurons of the hippocampal formation. These neurons receive excitatory glutamatergic afferents from the entorhinal cortex via the Angular Bundle/perforant path. In the present study, we tested whether electrophysiological stimulation of this glutamatergic pathway modifies NGF or BDNF messenger RNA (mRNA) expression in vivo. Within hours following brief trains of high frequency Angular Bundle stimulation, the levels of mRNA encoding both neurotrophins were increased exclusively in granule cells of the ipsilateral dentate gyrus. The increase in neurotrophic factor mRNA expression was found to be mediated through the N- methyl- d -aspartate (NMDA) glutamate receptor subtype, and occurred in the absence of seizure. These findings provide evidence that neurotrophic factor mRNA levels in the hippocampal formation are increased by direct activation of excitatory afferents originating in the entorhinal cortex. We suggest that the function of some neurotrophin-responsive neuronal populations may depend upon the integrity and activity of neurons in the entorhinal cortex, a population of neurons reported to be compromised in patients with Alzheimer's disease.
Maria Wagner - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous activation and opioid modulation of long-term potentiation in the dentate gyrus and the hippocampal CA3 region after stimulation of the perforant pathway in freely moving rats.
Brain research, 2001Co-Authors: Manfred Krug, Rudolf Brödemann, Maria WagnerAbstract:Abstract Recent investigations indicate monosynaptic activation by the perforant pathway (pp) of the dentate gyrus and the CA3 region. While short-term potentiation and long-term potentiation (LTP) and its opioid modulation are frequently described for the dentate gyrus, data for the CA3 region are rare. Therefore, evoked potentials and opioid modulation of LTP were directly compared in both target regions of the pp. Male Wistar rats were chronically implanted with a bipolar stimulation electrode in the pp (Angular Bundle) and two recording electrodes in the dorsal dentate gyrus and the CA3 region. Stimulation of the pp in the freely behaving animals induced short-latency evoked potentials in both target structures which were compared with respect to waveform, latency, amplitude and signs of short- and long-term neuronal plasticity. The short-latency potential in the CA3 region seemed to be a monosynaptic potential which displayed LTP sensitive to the N -methyl- d -aspartate receptor antagonist, MK 801, and depotentiating stimulation. After application of specific opioid antagonists at the μ-, δ- and κ-opioid receptor subtypes, naloxone, funaltrexamine, naltrindole and binaltorphimine, different effects on induction and maintenance of LTP of the population spike were found both within the dentate gyrus and between the dentate gyrus and the CA3 region. The results show marked diminution of LTP in the dentate gyrus only for naloxone and naltrindole and only small, if any, effects of naloxone on LTP in the CA3 region. Thus, neuronal plasticity in the direct perforant pathway input to the CA3 region seems not to be under such substantial opioidergic control. LTP would be inducible in that region even when LTP in the input formation, the dentate gyrus, and transsynaptic LTP via the mossy fibres are blocked.