title: Multiple episodes of sodium depletion in the rat: a remodeling of the electrical properties of median preoptic nucleus neurons.
abstract: 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.
authors.affiliation: Université Laval, Laurier, Québec, Canada.
authors.forename: Aurore N
authors.initials: AN
authors.lastname: Voisin
authors.forename: Didier
authors.initials: D
authors.lastname: Mouginot
authors.forename: Guy
authors.initials: G
authors.lastname: Drolet
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D008297:Male; D064587:Osmoregulation; D011301:Preoptic Area / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D011984:Sensory Receptor Cells / Q000378:metabolism / Q000502:physiology*; D012964:Sodium / Q000502:physiology*
chemical_list: D017450:Receptors, Opioid, mu; D012964:Sodium
keywords: lamina terminalis; mu-opioid receptors; sensitisation; sodium homeostasis