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Electrophysiology of Hypothalamic Magnocellular Neurons In vitro: A Rhythmic Drive in Organotypic Cultures and Acute Slices.

Israel JM, Oliet SH, Ciofi P - Front Neurosci (2016)

Bottom Line: Here, we have tested whether a similar hypothesis can be derived from in vitro experiments in acute slices of the adult hypothalamus.To this aim we have screened our electrophysiological recordings of the magnocellular neurons, previously obtained from acute slices, with an analysis of autocorrelation of action potentials to detect a rhythmic drive as we recently did for organotypic cultures.This confirmed that the bursting behavior of magnocellular neurons is governed by central pattern generator networks whose rhythmic drive, and thus probably integrity, is however less satisfactorily preserved in the acute slices from adult brains.

View Article: PubMed Central - PubMed

Affiliation: U1215, Neurocentre Magendie, Institut National de la Santé et de la Recherche MédicaleBordeaux, France; Université de BordeauxBordeaux, France.

ABSTRACT
Hypothalamic neurohormones are released in a pulsatile manner. The mechanisms of this pulsatility remain poorly understood and several hypotheses are available, depending upon the neuroendocrine system considered. Among these systems, hypothalamo-neurohypophyseal magnocellular neurons have been early-considered models, as they typically display an electrical activity consisting of bursts of action potentials that is optimal for the release of boluses of the neurohormones oxytocin and vasopressin. The cellular mechanisms underlying this bursting behavior have been studied in vitro, using either acute slices of the adult hypothalamus, or organotypic cultures of neonatal hypothalamic tissue. We have recently proposed, from experiments in organotypic cultures, that specific central pattern generator networks, upstream of magnocellular neurons, determine their bursting activity. Here, we have tested whether a similar hypothesis can be derived from in vitro experiments in acute slices of the adult hypothalamus. To this aim we have screened our electrophysiological recordings of the magnocellular neurons, previously obtained from acute slices, with an analysis of autocorrelation of action potentials to detect a rhythmic drive as we recently did for organotypic cultures. This confirmed that the bursting behavior of magnocellular neurons is governed by central pattern generator networks whose rhythmic drive, and thus probably integrity, is however less satisfactorily preserved in the acute slices from adult brains.

No MeSH data available.


Analogy between the locomotor and neuroendocrine circuits. Motor neurons and neuroendocrine cells are output units driven by central pattern generator (CPG) networks. CPGs generate the specific electrical firing required for secretion of neurotransmitters/neurohormones and the desired action of the effector structure: skeletal muscle for alpha-motor neurons, uterus and mammary myoepithelial cells in the case of magnocellular oxytocin (OT) neurons. The presumptive “OT-CPG” necessary for the milk-ejection reflex may be a two-level CPG comprising a rhythmogenic component in interaction with a pattern-forming component, the output of which being bursting activity. The secretomotor unit is mainly a follower of the CPG output triggering neurosecretion. BBB, blood-brain-barrier. For details, see the Conclusion.
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Figure 7: Analogy between the locomotor and neuroendocrine circuits. Motor neurons and neuroendocrine cells are output units driven by central pattern generator (CPG) networks. CPGs generate the specific electrical firing required for secretion of neurotransmitters/neurohormones and the desired action of the effector structure: skeletal muscle for alpha-motor neurons, uterus and mammary myoepithelial cells in the case of magnocellular oxytocin (OT) neurons. The presumptive “OT-CPG” necessary for the milk-ejection reflex may be a two-level CPG comprising a rhythmogenic component in interaction with a pattern-forming component, the output of which being bursting activity. The secretomotor unit is mainly a follower of the CPG output triggering neurosecretion. BBB, blood-brain-barrier. For details, see the Conclusion.

Mentions: Neuroendocrine cells are the final output neurons in their networks and have their targets outside the blood-brain-barrier. This arrangement early prompted an analogy with the output units of the locomotor circuits, i.e., the alpha motor neurons in the spinal cord (Harris, 1955; Markakis, 2002; Watts, 2015; Figure 7). More recently (Thompson and Swanson, 2003), an extensive analysis of intra-hypothalamic connectivity has proposed the existence of a meta-network responsible for the coordination of neuroendocrine and behavioral systems. This proposed “hypothalamic visceromotor pattern generator” (HVPG) network includes an extended CPG hosted by the rostral half of the periventricular continuum (PeV). As remarked by the authors, this disposition of the HVPG along a liquor compartment and near its motor targets indeed recalls the similar location of the spinal locomotor CPG along the central canal (Grillner, 2003; McCrea and Rybak, 2008), which reflects current efforts to comprehend the basic organization of the forebrain (Croizier et al., 2015).


Electrophysiology of Hypothalamic Magnocellular Neurons In vitro: A Rhythmic Drive in Organotypic Cultures and Acute Slices.

Israel JM, Oliet SH, Ciofi P - Front Neurosci (2016)

Analogy between the locomotor and neuroendocrine circuits. Motor neurons and neuroendocrine cells are output units driven by central pattern generator (CPG) networks. CPGs generate the specific electrical firing required for secretion of neurotransmitters/neurohormones and the desired action of the effector structure: skeletal muscle for alpha-motor neurons, uterus and mammary myoepithelial cells in the case of magnocellular oxytocin (OT) neurons. The presumptive “OT-CPG” necessary for the milk-ejection reflex may be a two-level CPG comprising a rhythmogenic component in interaction with a pattern-forming component, the output of which being bursting activity. The secretomotor unit is mainly a follower of the CPG output triggering neurosecretion. BBB, blood-brain-barrier. For details, see the Conclusion.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814512&req=5

Figure 7: Analogy between the locomotor and neuroendocrine circuits. Motor neurons and neuroendocrine cells are output units driven by central pattern generator (CPG) networks. CPGs generate the specific electrical firing required for secretion of neurotransmitters/neurohormones and the desired action of the effector structure: skeletal muscle for alpha-motor neurons, uterus and mammary myoepithelial cells in the case of magnocellular oxytocin (OT) neurons. The presumptive “OT-CPG” necessary for the milk-ejection reflex may be a two-level CPG comprising a rhythmogenic component in interaction with a pattern-forming component, the output of which being bursting activity. The secretomotor unit is mainly a follower of the CPG output triggering neurosecretion. BBB, blood-brain-barrier. For details, see the Conclusion.
Mentions: Neuroendocrine cells are the final output neurons in their networks and have their targets outside the blood-brain-barrier. This arrangement early prompted an analogy with the output units of the locomotor circuits, i.e., the alpha motor neurons in the spinal cord (Harris, 1955; Markakis, 2002; Watts, 2015; Figure 7). More recently (Thompson and Swanson, 2003), an extensive analysis of intra-hypothalamic connectivity has proposed the existence of a meta-network responsible for the coordination of neuroendocrine and behavioral systems. This proposed “hypothalamic visceromotor pattern generator” (HVPG) network includes an extended CPG hosted by the rostral half of the periventricular continuum (PeV). As remarked by the authors, this disposition of the HVPG along a liquor compartment and near its motor targets indeed recalls the similar location of the spinal locomotor CPG along the central canal (Grillner, 2003; McCrea and Rybak, 2008), which reflects current efforts to comprehend the basic organization of the forebrain (Croizier et al., 2015).

Bottom Line: Here, we have tested whether a similar hypothesis can be derived from in vitro experiments in acute slices of the adult hypothalamus.To this aim we have screened our electrophysiological recordings of the magnocellular neurons, previously obtained from acute slices, with an analysis of autocorrelation of action potentials to detect a rhythmic drive as we recently did for organotypic cultures.This confirmed that the bursting behavior of magnocellular neurons is governed by central pattern generator networks whose rhythmic drive, and thus probably integrity, is however less satisfactorily preserved in the acute slices from adult brains.

View Article: PubMed Central - PubMed

Affiliation: U1215, Neurocentre Magendie, Institut National de la Santé et de la Recherche MédicaleBordeaux, France; Université de BordeauxBordeaux, France.

ABSTRACT
Hypothalamic neurohormones are released in a pulsatile manner. The mechanisms of this pulsatility remain poorly understood and several hypotheses are available, depending upon the neuroendocrine system considered. Among these systems, hypothalamo-neurohypophyseal magnocellular neurons have been early-considered models, as they typically display an electrical activity consisting of bursts of action potentials that is optimal for the release of boluses of the neurohormones oxytocin and vasopressin. The cellular mechanisms underlying this bursting behavior have been studied in vitro, using either acute slices of the adult hypothalamus, or organotypic cultures of neonatal hypothalamic tissue. We have recently proposed, from experiments in organotypic cultures, that specific central pattern generator networks, upstream of magnocellular neurons, determine their bursting activity. Here, we have tested whether a similar hypothesis can be derived from in vitro experiments in acute slices of the adult hypothalamus. To this aim we have screened our electrophysiological recordings of the magnocellular neurons, previously obtained from acute slices, with an analysis of autocorrelation of action potentials to detect a rhythmic drive as we recently did for organotypic cultures. This confirmed that the bursting behavior of magnocellular neurons is governed by central pattern generator networks whose rhythmic drive, and thus probably integrity, is however less satisfactorily preserved in the acute slices from adult brains.

No MeSH data available.