The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Michael J. Mckinley - One of the best experts on this subject based on the ideXlab platform.
-
Neurons in the Median Preoptic Nucleus of the rat with collateral branches to the subfornical organ and supraoptic Nucleus
Brain research, 1992Co-Authors: Brian J. Oldfield, D.k. Hards, Michael J. MckinleyAbstract:A novel pathway between the subfornical organ and the supraoptic Nucleus involving the collateral branches of cell bodies situated in the lamina terminalis has been studied. Fluorogold was injected into the supraoptic Nucleus and rhodamine-labelled microspheres into the subfornical organ of rats. Nineteen % of neurons in the Median Preoptic Nucleus and 30% of neurons in the OVLT projecting to the subfornical organ also had axons extending to the supraoptic Nucleus. These pathways may represent a novel trajectory for the rely of information from the lamina terminalis to the supraoptic Nucleus.
-
Projections from the subfornical organ to the supraoptic Nucleus in the rat: ultrastructural identification of an interposed synapse in the Median Preoptic Nucleus using a combination of neuronal tracers.
Brain research, 1991Co-Authors: Brian J. Oldfield, D.k. Hards, Michael J. MckinleyAbstract:The subfornical organ, along with other regions of the lamina terminalis, may contain osmoreceptors and is likely to be a site of action of blood-borne angiotensin II. The neural pathways by which these stimuli lead to vasopressin secretion, have been suggested to extend from the subfornical organ to hypothalamic sites of vasopressin production either directly or via synapses in an intervening Nucleus such as the Median Preoptic Nucleus. In the present study, cholera toxin conjugated to horseradish peroxidase (CT/HRP) or colloidal gold (CT/Au) has been injected, respectively, into the subfornical organ and supraoptic Nucleus of the same animal. The anterograde and retrograde transport of the toxin from these two sites has made possible the identification, at the ultrastructural level, of a synapse in the Median Preoptic Nucleus interposed in the pathway between the subfornical organ and the supraoptic Nucleus. Moreover, the presence of retrogradely transported CT/HRP and CT/Au in the same neurone in the Median Preoptic Nucleus indicates that some neurones in this Nucleus have axons with collateral branches to both the subfornical organ and supraoptic Nucleus. Either or both of these pathways may transmit information related to the tonicity of the blood or circulating levels of angiotensin II to sites in the hypothalamus.
-
Median Preoptic Nucleus projections to vasopressin-containing neurones of the supraoptic Nucleus in sheep. A light and electron microscopic study.
Brain Research, 1991Co-Authors: Brian J. Oldfield, Richard R. Miselis, Michael J. MckinleyAbstract:It has been postulated that osmoreceptors are situated in either or both of two components of the lamina terminalis, the subfornical organ (sfo) and organum vasculosum laminae terminalis (ovlt) and that information from these sites may be relayed to the hypothalamus directly or via a synapse in the Median Preoptic Nucleus (mnpo). We have investigated the nature of projections from the mnpo to vasopressin (AVP)-containing neurones in the hypothalamus. Microinjections of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) have been made into the mnpo and supraoptic Nucleus (son) of the sheep. These injections indicated that in the sheep, as in the rat, the mnpo shares a reciprocal innervation with the sfo and ovlt. Furthermore, the most extensive efferent outflow of the mnpo is to the son, with lesser projections directed to the pvn and other hypothalamic sites. When examined at the electron microscopic level, fibres projecting from the mnpo to the son were found to form synapses with immunocytochemically identified AVP neurones. It is suggested that this pathway is one of the major routes by which information from putative osmoreceptors in the lamina terminalis is conveyed to AVP neurones in the hypothalamus.
Didier Mouginot - One of the best experts on this subject based on the ideXlab platform.
-
multiple episodes of sodium depletion in the rat a remodeling of the electrical properties of Median Preoptic Nucleus neurons
European Journal of Neuroscience, 2013Co-Authors: A. N. Voisin, Didier Mouginot, Guy DroletAbstract:In rat brain, the detection and integration of chemosensory and neural signals are achieved, inter alia, by the Median Preoptic Nucleus (MnPO) during a disturbance of the hydromineral balance. This is allowed through the presence of the sodium (Na(+) ) sensor neurons. Interestingly, enkephalins and mu-opioid receptors (μ-ORs) are known for their role in ingestive behaviors and have previously been shown to regulate the excitability of MnPO neurons following a single Na(+) depletion. However, little is known about the role of these μ-ORs in the response enhancement following repeated Na(+) challenge. Therefore, we used whole-cell recordings in acute brain slices to determine neuronal plasticity in the electrical properties of the MnPO Na(+) sensor-specific neuronal population following multiple Na(+) depletions. Our results show that the population of Na(+) sensor neurons was represented by 80% of MnPO neurons after a single Na(+) depletion and was reduced after three Na(+) depletions. Interestingly, the subpopulation of Na(+) sensors responding to D-Ala(2) ,N-MePhe(4) ,Gly-ol-enkephalin (DAMGO), a specific μ-OR agonist, represented 11% of MnPO neurons after a single Na(+) depletion and the population doubled after three Na(+) depletions. Moreover, Na(+) sensor neurons displayed modifications in the discharge pattern distribution and shape of calcium action potentials after three Na(+) depletions but these changes did not occur in Na(+) sensors responding to DAMGO. Thus, the reinforced μ-OR functionality in Na(+) sensors might take place to control the neuronal hyperexcitability and this plasticity in opioid-sensitive and Na(+) detection MnPO networks might sustain the enhanced salt ingestion induced by repeated exposure to Na(+) depletion.
-
Intrinsic properties of the sodium sensor neurons in the rat Median Preoptic Nucleus
AJP: Regulatory Integrative and Comparative Physiology, 2012Co-Authors: A. N. Voisin, Guy Drolet, Didier MouginotAbstract:The essential role of the Median Preoptic Nucleus (MnPO) in the integration of chemosensory information associated with the hydromineral state of the rat relies on the presence of a unique population of sodium (Na+) sensor neurons. Little is known about the intrinsic properties of these neurons; therefore, we used whole cell recordings in acute brain slices to determine the electrical fingerprints of this specific neural population of rat MnPO. The data collected from a large sample of neurons (115) indicated that the Na+ sensor neurons represent a majority of the MnPO neurons in situ (83%). These neurons displayed great diversity in both firing patterns induced by transient depolarizing current steps and rectifying properties activated by hyperpolarizing current steps. This diversity of electrical properties was also present in non-Na+ sensor neurons. Subpopulations of Na+ sensor neurons could be distinguished, however, from the non-Na+ sensor neurons. The firing frequency was higher in Na+ sensor neurons, showing irregular spike discharges, and the amplitude of the time-dependent rectification was weaker in the Na+ sensor neurons than in non-Na+ sensor neurons. The diversity among the electrical properties of the MnPO neurons contrasts with the relative function homogeneity (Na+ sensing). However, this diversity might be correlated with a variety of direct synaptic connections linking the MnPO to different brain areas involved in various aspects of the restoration and conservation of the body fluid homeostasis.
-
neuronal sodium leak channel is responsible for the detection of sodium in the rat Median Preoptic Nucleus
Journal of Neurophysiology, 2011Co-Authors: Christina Tremblay, Melaine Henry, Emmanuelle Berret, Benjamin Nehme, Louis Nadeau, Didier MouginotAbstract:Sodium (Na+) ions are of primary importance for hydromineral and cardiovascular homeostasis, and the level of Na+ in the body fluid compartments [plasma and cerebrospinal fluid (CSF)] is precisely ...
-
endogenous angiotensin ii facilitates gabaergic neurotransmission afferent to the na responsive neurons of the rat Median Preoptic Nucleus
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2009Co-Authors: Melaine Henry, Magali Grob, Didier MouginotAbstract:The Median Preoptic Nucleus (MnPO) is densely innervated by efferent projections from the subfornical organ (SFO) and, therefore, is an important relay for the peripheral chemosensory and humoral information (osmolality and serum levels ANG II). In this context, controlling the excitability of MnPO neuronal populations is a major determinant of body fluid homeostasis and cardiovascular regulation. Using a brain slice preparation and patch-clamp recordings, our study sought to determine whether endogenous ANG II modulates the strength of the SFO-derived GABAergic inputs to the MnPO. Our results showed that the amplitude of the inhibitory postsynaptic currents (IPSCs) were progressively reduced by 44 +/- 2.3% by (Sar(1), Ile(8))-ANG II, a competitive ANG type 1 receptor (AT(1)R) antagonist. Similarly, losartan, a nonpeptidergic AT(1)R antagonist decreased the IPSC amplitude by 40.4 +/- 5.6%. The facilitating effect of endogenous ANG II on the GABAergic input to the MnPO was not attributed to a change in GABA release probability and was mimicked by exogenous ANG II, which potentiated the amplitude of the muscimol-activated GABA(A)/Cl(-) current by 53.1 +/- 11.4%. These results demonstrate a postsynaptic locus of action of ANG II. Further analysis reveals that ANG II did not affect the reversal potential of the synaptic inhibitory response, thus privileging a cross talk between postsynaptic AT(1) and GABA(A) receptors. Interestingly, facilitation of GABAergic neurotransmission by endogenous ANG II was specific to neurons responding to changes in the ambient Na(+) level. This finding, combined with the ANG II-mediated depolarization of non-Na(+)-responsive neurons reveals the dual actions of ANG II to modulate the excitability of MnPO neurons.
-
postsynaptic µ opioid receptor response in the Median Preoptic Nucleus is altered by a systemic sodium challenge in rats
European Journal of Neuroscience, 2008Co-Authors: Melaine Henry, Guy Drolet, Didier MouginotAbstract:The Median Preoptic Nucleus (MnPO) is an integrator site for the chemosensory and neural signals induced by a perturbation in the hydromineral balance, and it is highly involved in controlling fluid and electrolyte ingestion. Here, we hypothesize that opioid peptides, previously recognized to control ingestive behaviors, may regulate the excitability of MnPO neurons and that this regulatory action may depend on the natriuric (Na(+)) status of body fluid compartments. Our results show that activation of mu-, but not delta-, opioid receptors (OR) triggered a membrane hyperpolarization by recruiting a G-protein-regulated inward-rectifier K(+) (GIRK) conductance in 41% of the neurons tested. Interestingly, 24 h Na(+) depletion strengthened this opioid-mediated control of neuronal excitability. In Na(+)-depleted animals, the neuronal population displaying the mu-OR-induced hyperpolarization expanded to 60% (Z-test, P = 0.012), whereas Na(+) repletion restored this population to the control level (39%; Z-test, P = 0.037). Among the neurons displaying mu-OR-induced hyperpolarization, Na(+) depletion specifically increased the neuronal population responsive to variation in ambient Na(+) (from 27% to 43%; Z-test, P = 0.029). In contrast, Na(+) repletion dramatically reduced the population that was unresponsive to Na(+) (from 17% to 3%; Z-test, P = 0.031). Neither the basic properties of the neurons nor the characteristics of the mu-OR-induced response were altered by the body Na(+) challenge. Our results indicate that an episode of Na(+) depletion/Na(+) repletion modifies the organization of the opioid-sensitive network of the MnPO. Such network plasticity might be related to the avid salt ingestion triggered by repeated Na(+) depletion.
Ronald Szymusiak - One of the best experts on this subject based on the ideXlab platform.
-
inactivation of Median Preoptic Nucleus causes c fos expression in hypocretin and serotonin containing neurons in anesthetized rat
Brain Research, 2008Co-Authors: Dennis Mcginty, Ronald Szymusiak, Natalia Suntsova, Sunil Kumar, Tariq Bashir, Seema Rai, Md Noor AlamAbstract:Abstract The Median Preoptic Nucleus (MnPN) of the hypothalamus contains sleep-active neurons including sleep-active GABAergic neurons and is involved in the regulation of nonREM/REM sleep. The hypocretinergic (HCRT) neurons of the perifornical-lateral hypothalamic area (PF-LHA) and serotonergic (5-HT) neurons of the dorsal raphe Nucleus (DRN) are mostly active during waking and have been implicated in the regulation of arousal. MnPN GABAergic neurons project to the PF-LHA and DRN. It is hypothesized that MnPN promotes sleep by inhibiting multiple arousal systems including HCRT and other wake-active neurons within the PF-LHA and 5-HT neurons in the DRN. We examined the effects of inactivation of MnPN neurons by locally microinjecting 0.2 µl of 1 mM or 10 mM solutions of a GABA A receptor agonist, muscimol, into the MnPN on Fos expression (Fos-IR) in the PF-LHA neurons including HCRT neurons and 5-HT neurons in the DRN in anesthetized rats. Compared to artificial cerebrospinal fluid control, microinjection of muscimol into the MnPN resulted in significantly higher percentages of HCRT and non-HCRT neurons in the PF-LHA and 5-HT neurons in the DRN that exhibited Fos-IR. The percentage of melanin-concentrating hormone (MCH)+/Fos+ neurons in the PF-LHA did not change after muscimol treatments. These results support a hypothesis that the activation of MnPN neurons contributes to the suppression of wake-promoting systems including HCRT and other unidentified neurons in the PF-LHA and 5-HT neurons in the DRN. These results also suggest that MCH neurons may not be under MnPN inhibitory control. These findings are consistent with a hypothesized role of MnPN in sleep regulation.
-
Efferent projections from the Median Preoptic Nucleus to sleep- and arousal-regulatory nuclei in the rat brain.
Neuroscience, 2007Co-Authors: Aaron Uschakov, Dennis Mcginty, Hui Gong, Ronald SzymusiakAbstract:Abstract The Median Preoptic Nucleus (MnPO) has been implicated in the regulation of hydromineral balance and cardiovascular regulation. The MnPO also contains neurons that are active during sleep and in response to increasing homeostatic pressure for sleep. The potential role of these neurons in the regulation of arousal prompted an analysis of the efferent projections from the MnPO. Anterograde and retrograde neuroanatomical tracers were utilized to characterize the neural connectivity from the MnPO to several functionally important sleep- and arousal-regulatory neuronal systems in the rat brain. Anterograde terminal labeling from the MnPO was confirmed within the core and extended ventrolateral Preoptic Nucleus. Within the lateral hypothalamus, labeled axons were observed in close apposition to proximal and distal dendrites of hypocretin/orexin immunoreactive (IR) cells. Projections from the MnPO to the locus coeruleus were observed within and surrounding the tyrosine hydroxylase–IR cell cluster. Labeled axons from the MnPO were mostly observed within the lateral division of the dorsal raphe Nucleus and heavily within the ventrolateral periaqueductal gray. Few anterogradely labeled appositions were present juxtaposed to choline acetyltransferase–IR somata within the magnocellular Preoptic area. The use of retrogradely transported neuroanatomical tracers placed within the prospective efferent terminal fields supported and confirmed findings from the anterograde tracer experiments. These anatomical findings support the hypothesis that MnPO neurons function to promote sleep by inhibition of orexinergic and monoaminergic arousal systems and disinhibition of sleep regulatory neurons in the ventrolateral Preoptic area.
-
the Median Preoptic Nucleus reciprocally modulates activity of arousal related and sleep related neurons in the perifornical lateral hypothalamus
The Journal of Neuroscience, 2007Co-Authors: Natalia Suntsova, Ronald Szymusiak, Md Noor Alam, Sunil Kumar, Ruben Guzmanmarin, Dennis McgintyAbstract:The perifornical–lateral hypothalamic area (PF/LH) contains neuronal groups playing an important role in control of waking and sleep. Among the brain regions that regulate behavioral states, one of the strongest sources of projections to the PF/LH is the Median Preoptic Nucleus (MnPN) containing a sleep-active neuronal population. To evaluate the role of MnPN afferents in the control of PF/LH neuronal activity, we studied the responses of PF/LH cells to electrical stimulation or local chemical manipulation of the MnPN in freely moving rats. Single-pulse electrical stimulation evoked responses in 79% of recorded PF/LH neurons. No cells were activated antidromically. Direct and indirect transynaptic effects depended on sleep–wake discharge pattern of PF/LH cells. The majority of arousal-related neurons, that is, cells discharging at maximal rates during active waking (AW) or during AW and rapid eye movement (REM) sleep, exhibited exclusively or initially inhibitory responses to stimulation. Sleep-related neurons, the cells with elevated discharge during non-REM and REM sleep or selectively active in REM sleep, exhibited exclusively or initially excitatory responses. Activation of the MnPN via microdialytic application of l-glutamate or bicuculline resulted in reduced discharge of arousal-related and in excitation of sleep-related PF/LH neurons. Deactivation of the MnPN with muscimol caused opposite effects. The results indicate that the MnPN contains subset(s) of neurons, which exert inhibitory control over arousal-related and excitatory control over sleep-related PF/LH neurons. We hypothesize that MnPN sleep-active neuronal group has both inhibitory and excitatory outputs that participate in the inhibitory control of arousal-promoting PF/LH mechanisms.
-
different neuronal populations of the rat Median Preoptic Nucleus express c fos during sleep and in response to hypertonic saline or angiotensin ii
The Journal of Physiology, 2005Co-Authors: I Gvilia, Dennis Mcginty, C Angara, Ronald SzymusiakAbstract:The Median Preoptic Nucleus (MnPN) of the hypothalamus contains sleep-active neurones, and sleep-related Fos-immunoreactivity (IR) in this Nucleus is primarily expressed in GABAergic cells. The MnPN also contains cells responsive to hypertonic saline and to angiotensin-II (Ang-II). To clarify functional relationships between MnPN neurones involved in the regulation of sleep and body fluid homeostasis, we examined c-fos expression in the MnPN after administration of hypertonic saline and Ang-II in both spontaneously sleeping and sleep-deprived rats. Systemic administration of hypertonic saline and intracerebroventricular (i.c.v.) injection of Ang-II increased Fos-IR in both spontaneously sleeping and sleep-deprived rats, compared to control animals. To determine if the population of MnPN neurones activated in response to osmotic and hormonal stimuli is similar to or different from neurones activated during sleep, we quantified Fos-IR in MnPN GABAergic neurones in spontaneously sleeping hypertonic saline- and Ang-II-treated rats versus respective control rats. Fos-IR evoked by these treatments occurred primarily (80–85%) in non-GABAergic neurones. Findings of the present study provide evidence that separate populations of MnPN neurones are involved in the regulation of sleep and body fluid homeostasis.
-
sleep promoting functions of the hypothalamic Median Preoptic Nucleus inhibition of arousal systems
Archives Italiennes De Biologie, 2004Co-Authors: Dennis Mcginty, Natalia Suntsova, Md Noor Alam, Hui Gong, Melvi Methippara, R Guzmanmarin, Ronald SzymusiakAbstract:Recent work supports the hypotheses developed by von Economo and Nauta and elaborated by Sallanon et al. that the POA contains a sleep-promoting output that opposes wake-promoting neuronal groups in the PH. The POA gives rise to descending pathways that terminate within wake-promoting populations in pLH, PH and midbrain. Current evidence suggests that this output originates in POA sleep-active GABAergic neurons. This output also seems to convey the signals of homeostatic drive. Disynaptic projections from the SCN to both MnPN and VLPO were recently identified. These may regulate the circadian control of sleep propensity. The hypothesis that the descending projections from POA sleep-active neurons to sites of arousal-related neurons originates in GABAergic neurons must be confirmed. Also to be further clarified is the anatomical distribution of putative sleep-active GABAergic neurons within the POA. Segregated groups have been found in the MnPN and VLPO, but unit recording studies of sleep-active neurons, lesion studies and local neurochemical application studies all indicate that sleep-active neurons may be found diffusely in the POA and adjacent areas. The MnPN has been shown previously to be involved in water balance and blood pressure regulation and to be responsive to hyperthermia. Our studies suggest that this Nucleus also contains sleep-active, putative sleep-promoting neurons. However, interactions between sleep control and physiological variables must be considered. In particular, the details of neuronal basis of the coupling of warm-sensitive neurons in MnPN to the POA hypnogenic output has not been explored. It is also worth noting that both the VLPO and MnPN lie close to the ventricular and subarachnoid surface and are punctuated by radial arterioles. The possibility that the sleep-regulatory functions of these sites is coupled to physiological signals conveyed through epithelial cells has been suggested for the actions of PGD2 but has yet to be explored in detail for other putative hypnogens.
Dennis Mcginty - One of the best experts on this subject based on the ideXlab platform.
-
inactivation of Median Preoptic Nucleus causes c fos expression in hypocretin and serotonin containing neurons in anesthetized rat
Brain Research, 2008Co-Authors: Dennis Mcginty, Ronald Szymusiak, Natalia Suntsova, Sunil Kumar, Tariq Bashir, Seema Rai, Md Noor AlamAbstract:Abstract The Median Preoptic Nucleus (MnPN) of the hypothalamus contains sleep-active neurons including sleep-active GABAergic neurons and is involved in the regulation of nonREM/REM sleep. The hypocretinergic (HCRT) neurons of the perifornical-lateral hypothalamic area (PF-LHA) and serotonergic (5-HT) neurons of the dorsal raphe Nucleus (DRN) are mostly active during waking and have been implicated in the regulation of arousal. MnPN GABAergic neurons project to the PF-LHA and DRN. It is hypothesized that MnPN promotes sleep by inhibiting multiple arousal systems including HCRT and other wake-active neurons within the PF-LHA and 5-HT neurons in the DRN. We examined the effects of inactivation of MnPN neurons by locally microinjecting 0.2 µl of 1 mM or 10 mM solutions of a GABA A receptor agonist, muscimol, into the MnPN on Fos expression (Fos-IR) in the PF-LHA neurons including HCRT neurons and 5-HT neurons in the DRN in anesthetized rats. Compared to artificial cerebrospinal fluid control, microinjection of muscimol into the MnPN resulted in significantly higher percentages of HCRT and non-HCRT neurons in the PF-LHA and 5-HT neurons in the DRN that exhibited Fos-IR. The percentage of melanin-concentrating hormone (MCH)+/Fos+ neurons in the PF-LHA did not change after muscimol treatments. These results support a hypothesis that the activation of MnPN neurons contributes to the suppression of wake-promoting systems including HCRT and other unidentified neurons in the PF-LHA and 5-HT neurons in the DRN. These results also suggest that MCH neurons may not be under MnPN inhibitory control. These findings are consistent with a hypothesized role of MnPN in sleep regulation.
-
Efferent projections from the Median Preoptic Nucleus to sleep- and arousal-regulatory nuclei in the rat brain.
Neuroscience, 2007Co-Authors: Aaron Uschakov, Dennis Mcginty, Hui Gong, Ronald SzymusiakAbstract:Abstract The Median Preoptic Nucleus (MnPO) has been implicated in the regulation of hydromineral balance and cardiovascular regulation. The MnPO also contains neurons that are active during sleep and in response to increasing homeostatic pressure for sleep. The potential role of these neurons in the regulation of arousal prompted an analysis of the efferent projections from the MnPO. Anterograde and retrograde neuroanatomical tracers were utilized to characterize the neural connectivity from the MnPO to several functionally important sleep- and arousal-regulatory neuronal systems in the rat brain. Anterograde terminal labeling from the MnPO was confirmed within the core and extended ventrolateral Preoptic Nucleus. Within the lateral hypothalamus, labeled axons were observed in close apposition to proximal and distal dendrites of hypocretin/orexin immunoreactive (IR) cells. Projections from the MnPO to the locus coeruleus were observed within and surrounding the tyrosine hydroxylase–IR cell cluster. Labeled axons from the MnPO were mostly observed within the lateral division of the dorsal raphe Nucleus and heavily within the ventrolateral periaqueductal gray. Few anterogradely labeled appositions were present juxtaposed to choline acetyltransferase–IR somata within the magnocellular Preoptic area. The use of retrogradely transported neuroanatomical tracers placed within the prospective efferent terminal fields supported and confirmed findings from the anterograde tracer experiments. These anatomical findings support the hypothesis that MnPO neurons function to promote sleep by inhibition of orexinergic and monoaminergic arousal systems and disinhibition of sleep regulatory neurons in the ventrolateral Preoptic area.
-
the Median Preoptic Nucleus reciprocally modulates activity of arousal related and sleep related neurons in the perifornical lateral hypothalamus
The Journal of Neuroscience, 2007Co-Authors: Natalia Suntsova, Ronald Szymusiak, Md Noor Alam, Sunil Kumar, Ruben Guzmanmarin, Dennis McgintyAbstract:The perifornical–lateral hypothalamic area (PF/LH) contains neuronal groups playing an important role in control of waking and sleep. Among the brain regions that regulate behavioral states, one of the strongest sources of projections to the PF/LH is the Median Preoptic Nucleus (MnPN) containing a sleep-active neuronal population. To evaluate the role of MnPN afferents in the control of PF/LH neuronal activity, we studied the responses of PF/LH cells to electrical stimulation or local chemical manipulation of the MnPN in freely moving rats. Single-pulse electrical stimulation evoked responses in 79% of recorded PF/LH neurons. No cells were activated antidromically. Direct and indirect transynaptic effects depended on sleep–wake discharge pattern of PF/LH cells. The majority of arousal-related neurons, that is, cells discharging at maximal rates during active waking (AW) or during AW and rapid eye movement (REM) sleep, exhibited exclusively or initially inhibitory responses to stimulation. Sleep-related neurons, the cells with elevated discharge during non-REM and REM sleep or selectively active in REM sleep, exhibited exclusively or initially excitatory responses. Activation of the MnPN via microdialytic application of l-glutamate or bicuculline resulted in reduced discharge of arousal-related and in excitation of sleep-related PF/LH neurons. Deactivation of the MnPN with muscimol caused opposite effects. The results indicate that the MnPN contains subset(s) of neurons, which exert inhibitory control over arousal-related and excitatory control over sleep-related PF/LH neurons. We hypothesize that MnPN sleep-active neuronal group has both inhibitory and excitatory outputs that participate in the inhibitory control of arousal-promoting PF/LH mechanisms.
-
different neuronal populations of the rat Median Preoptic Nucleus express c fos during sleep and in response to hypertonic saline or angiotensin ii
The Journal of Physiology, 2005Co-Authors: I Gvilia, Dennis Mcginty, C Angara, Ronald SzymusiakAbstract:The Median Preoptic Nucleus (MnPN) of the hypothalamus contains sleep-active neurones, and sleep-related Fos-immunoreactivity (IR) in this Nucleus is primarily expressed in GABAergic cells. The MnPN also contains cells responsive to hypertonic saline and to angiotensin-II (Ang-II). To clarify functional relationships between MnPN neurones involved in the regulation of sleep and body fluid homeostasis, we examined c-fos expression in the MnPN after administration of hypertonic saline and Ang-II in both spontaneously sleeping and sleep-deprived rats. Systemic administration of hypertonic saline and intracerebroventricular (i.c.v.) injection of Ang-II increased Fos-IR in both spontaneously sleeping and sleep-deprived rats, compared to control animals. To determine if the population of MnPN neurones activated in response to osmotic and hormonal stimuli is similar to or different from neurones activated during sleep, we quantified Fos-IR in MnPN GABAergic neurones in spontaneously sleeping hypertonic saline- and Ang-II-treated rats versus respective control rats. Fos-IR evoked by these treatments occurred primarily (80–85%) in non-GABAergic neurones. Findings of the present study provide evidence that separate populations of MnPN neurones are involved in the regulation of sleep and body fluid homeostasis.
-
sleep promoting functions of the hypothalamic Median Preoptic Nucleus inhibition of arousal systems
Archives Italiennes De Biologie, 2004Co-Authors: Dennis Mcginty, Natalia Suntsova, Md Noor Alam, Hui Gong, Melvi Methippara, R Guzmanmarin, Ronald SzymusiakAbstract:Recent work supports the hypotheses developed by von Economo and Nauta and elaborated by Sallanon et al. that the POA contains a sleep-promoting output that opposes wake-promoting neuronal groups in the PH. The POA gives rise to descending pathways that terminate within wake-promoting populations in pLH, PH and midbrain. Current evidence suggests that this output originates in POA sleep-active GABAergic neurons. This output also seems to convey the signals of homeostatic drive. Disynaptic projections from the SCN to both MnPN and VLPO were recently identified. These may regulate the circadian control of sleep propensity. The hypothesis that the descending projections from POA sleep-active neurons to sites of arousal-related neurons originates in GABAergic neurons must be confirmed. Also to be further clarified is the anatomical distribution of putative sleep-active GABAergic neurons within the POA. Segregated groups have been found in the MnPN and VLPO, but unit recording studies of sleep-active neurons, lesion studies and local neurochemical application studies all indicate that sleep-active neurons may be found diffusely in the POA and adjacent areas. The MnPN has been shown previously to be involved in water balance and blood pressure regulation and to be responsive to hyperthermia. Our studies suggest that this Nucleus also contains sleep-active, putative sleep-promoting neurons. However, interactions between sleep control and physiological variables must be considered. In particular, the details of neuronal basis of the coupling of warm-sensitive neurons in MnPN to the POA hypnogenic output has not been explored. It is also worth noting that both the VLPO and MnPN lie close to the ventricular and subarachnoid surface and are punctuated by radial arterioles. The possibility that the sleep-regulatory functions of these sites is coupled to physiological signals conveyed through epithelial cells has been suggested for the actions of PGD2 but has yet to be explored in detail for other putative hypnogens.
Brian J. Oldfield - One of the best experts on this subject based on the ideXlab platform.
-
Neurons in the Median Preoptic Nucleus of the rat with collateral branches to the subfornical organ and supraoptic Nucleus
Brain research, 1992Co-Authors: Brian J. Oldfield, D.k. Hards, Michael J. MckinleyAbstract:A novel pathway between the subfornical organ and the supraoptic Nucleus involving the collateral branches of cell bodies situated in the lamina terminalis has been studied. Fluorogold was injected into the supraoptic Nucleus and rhodamine-labelled microspheres into the subfornical organ of rats. Nineteen % of neurons in the Median Preoptic Nucleus and 30% of neurons in the OVLT projecting to the subfornical organ also had axons extending to the supraoptic Nucleus. These pathways may represent a novel trajectory for the rely of information from the lamina terminalis to the supraoptic Nucleus.
-
Projections from the subfornical organ to the supraoptic Nucleus in the rat: ultrastructural identification of an interposed synapse in the Median Preoptic Nucleus using a combination of neuronal tracers.
Brain research, 1991Co-Authors: Brian J. Oldfield, D.k. Hards, Michael J. MckinleyAbstract:The subfornical organ, along with other regions of the lamina terminalis, may contain osmoreceptors and is likely to be a site of action of blood-borne angiotensin II. The neural pathways by which these stimuli lead to vasopressin secretion, have been suggested to extend from the subfornical organ to hypothalamic sites of vasopressin production either directly or via synapses in an intervening Nucleus such as the Median Preoptic Nucleus. In the present study, cholera toxin conjugated to horseradish peroxidase (CT/HRP) or colloidal gold (CT/Au) has been injected, respectively, into the subfornical organ and supraoptic Nucleus of the same animal. The anterograde and retrograde transport of the toxin from these two sites has made possible the identification, at the ultrastructural level, of a synapse in the Median Preoptic Nucleus interposed in the pathway between the subfornical organ and the supraoptic Nucleus. Moreover, the presence of retrogradely transported CT/HRP and CT/Au in the same neurone in the Median Preoptic Nucleus indicates that some neurones in this Nucleus have axons with collateral branches to both the subfornical organ and supraoptic Nucleus. Either or both of these pathways may transmit information related to the tonicity of the blood or circulating levels of angiotensin II to sites in the hypothalamus.
-
Median Preoptic Nucleus projections to vasopressin-containing neurones of the supraoptic Nucleus in sheep. A light and electron microscopic study.
Brain Research, 1991Co-Authors: Brian J. Oldfield, Richard R. Miselis, Michael J. MckinleyAbstract:It has been postulated that osmoreceptors are situated in either or both of two components of the lamina terminalis, the subfornical organ (sfo) and organum vasculosum laminae terminalis (ovlt) and that information from these sites may be relayed to the hypothalamus directly or via a synapse in the Median Preoptic Nucleus (mnpo). We have investigated the nature of projections from the mnpo to vasopressin (AVP)-containing neurones in the hypothalamus. Microinjections of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) have been made into the mnpo and supraoptic Nucleus (son) of the sheep. These injections indicated that in the sheep, as in the rat, the mnpo shares a reciprocal innervation with the sfo and ovlt. Furthermore, the most extensive efferent outflow of the mnpo is to the son, with lesser projections directed to the pvn and other hypothalamic sites. When examined at the electron microscopic level, fibres projecting from the mnpo to the son were found to form synapses with immunocytochemically identified AVP neurones. It is suggested that this pathway is one of the major routes by which information from putative osmoreceptors in the lamina terminalis is conveyed to AVP neurones in the hypothalamus.