title: Hindbrain oxytocin receptors contribute to the effects of circulating oxytocin on food intake in male rats.
abstract: Oxytocin (OT)-elicited hypophagia has been linked to neural activity in the nucleus of the solitary tract (NTS). Because plasma OT levels increase after a meal, we hypothesized that circulating OT acts at both peripheral and hindbrain OT receptors (OTRs) to limit food intake. To initially determine whether circulating OT inhibits food intake by acting at hindbrain OTRs, we pretreated rats with an OTR antagonist administered into the fourth ventricle (4V) followed by either central or systemic OT administration. Administration of the OTR antagonist into the 4V blocked anorexia induced by either 4V or i.p. injection of OT. However, blockade of peripheral OTRs also weakened the anorectic response to ip OT. Our data suggest a predominant role for hindbrain OTRs in the hypophagic response to peripheral OT administration. To elucidate central mechanisms of OT hypophagia, we tested whether OT activates NTS catecholaminergic neurons. OT (ip) increased the number of NTS cells expressing c-Fos, of which 10%-15% were catecholaminergic. Furthermore, electrophysiological studies in mice revealed that OT stimulated 47% (8 of 17) of NTS catecholamine neurons through a presynaptic mechanism. However, OT-elicited hypophagia did not appear to require activation of α1-adrenoceptors, and blockade of glucagon-like peptide-1 receptors similarly did not attenuate anorexia induced by OT. These findings demonstrate that OT elicits satiety through both central and peripheral OTRs and that although catecholamine neurons are a downstream target of OT signaling in the NTS, the hypophagic effect is mediated independently of α1-adrenoceptor signaling.
authors.affiliation: Research and Development Service (J.M.H., V.T.A., B.W.T., R.W.C., B.H.H., D.G.B., J.E.B.), Veterans Affairs Puget Sound Health Care System, Seattle, Washington 98108; Department of Medicine (J.M.H., G.J.M., M.W.S., D.G.B., J.E.B.), Division of Metabolism, Endocrinology, and Nutrition, and Diabetes and Obesity Center of Excellence (G.J.M., M.W.S.), Department of Medicine, University of Washington, Seattle, Washington 98195; Program in Neuroscience (M.Z., S.M.A.), Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, Washington 99164.
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Ho
authors.forename: Vishwanath T
authors.initials: VT
authors.lastname: Anekonda
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Thompson
authors.forename: Mingyan
authors.initials: M
authors.lastname: Zhu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Curry
authors.forename: Bang H
authors.initials: BH
authors.lastname: Hwang
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Morton
authors.forename: Michael W
authors.initials: MW
authors.lastname: Schwartz
authors.forename: Denis G
authors.initials: DG
authors.lastname: Baskin
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Appleyard
authors.forename: James E
authors.initials: JE
authors.lastname: Blevins
mesh_terms: D000818:Animals; D002395:Catecholamines / Q000502:physiology; D004435:Eating / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005260:Female; D052216:Glucagon-Like Peptide 1 / Q000037:antagonists & inhibitors / Q000502:physiology; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010121:Oxytocin / Q000502:physiology*; D010446:Peptide Fragments / Q000502:physiology; D011224:Prazosin; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D018045:Receptors, Oxytocin / Q000502:physiology*; D017552:Solitary Nucleus / Q000502:physiology*; D015430:Weight Gain / Q000502:physiology
chemical_list: D002395:Catecholamines; D010446:Peptide Fragments; D018045:Receptors, Oxytocin; D010121:Oxytocin; C083773:exendin (9-39); D052216:Glucagon-Like Peptide 1; D011224:Prazosin