Serotonergic mechanisms of the lateral parabrachial nucleus and cholinergic-induced sodium appetite.
Central cholinergic mechanisms are suggested to participate in osmoreceptor-induced water intake. Therefore, central injections of the cholinergic agonist carbachol usually produce water intake (i.e., thirst) and are ineffective in inducing the intake of hypertonic saline solutions (i.e., the operational definition of sodium appetite). Recent studies have indicated that bilateral injections of the serotonin receptor antagonist methysergide into the lateral parabrachial nucleus (LPBN) markedly increases salt intake in models involving the activation of the renin-angiotensin system or mineralocorticoid hormones. The present studies investigated whether sodium appetite could be induced by central cholinergic activation with carbachol (an experimental condition where only water is typically ingested) after the blockade of LPBN serotonergic mechanisms with methysergide treatment in rats. When administered intracerebroventricularly in combination with injections of vehicle into both LPBN, carbachol (4 nmol) caused water drinking but insignificant intake of hypertonic saline. In contrast, after bilateral LPBN injections of methysergide (4 microg), intracerebroventricular carbachol induced the intake of 0.3 M NaCl. Water intake stimulated by intracerebroventricular carbachol was not changed by LPBN methysergide injections. The results indicate that central cholinergic activation can induce marked intake of hypertonic NaCl if the inhibitory serotonergic mechanisms of the LPBN are attenuated.
Menani
José Vanderlei
JV
Department of Psychology, University of Iowa, Iowa City, Iowa 52242-1407, USA.
Barbosa
Silas Pereira
SP
De Luca
Laurival Antonio
LA
De Gobbi
Juliana Irani Fratucci
JI
Johnson
Alan Kim
AK
D000818:Animals; D001066:Appetite / Q000187:drug effects / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D002799:Cholinergic Fibers / Q000502:physiology*; D004326:Drinking / Q000187:drug effects; D007267:Injections; D007276:Injections, Intraventricular; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012249:Rhombencephalon / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D012964:Sodium; D012965:Sodium Chloride
D018679:Cholinergic Agonists; D012702:Serotonin Antagonists; D012701:Serotonin; D012965:Sodium Chloride; D002217:Carbachol; D012964:Sodium; D008784:Methysergide