title: Oxytocin action in the ventral tegmental area affects sucrose intake.
abstract: Brain oxytocin is known to play a role in the control of food intake, and recent studies suggest that stimulation of central oxytocin receptors selectively suppresses carbohydrate intake. The specific oxytocin projection sites and receptor populations involved in this response are as yet unidentified. We hypothesized that oxytocin receptors in the ventral tegmental area (VTA) may play a role in limiting sucrose intake, because the VTA is known to influence palatable food intake. We first performed a dose response study in which we observed that intra-VTA oxytocin injection significantly suppressed intake of a 10% sucrose solution during a 30-min test session by 13.35-20.5% relative to vehicle treatment. Doses of intra-VTA oxytocin that suppressed sucrose intake had no effect on water intake. Next we examined the effects of two oxytocin receptor antagonists, (d(CH2)5(1),Tyr(Me)(2),Orn(8))-Oxytocin (OVT) and L-368,899. Each of these antagonists significantly increased 10% sucrose intake by 17-20.5% relative to vehicle when delivered directly into the VTA, at doses subthreshold for effect if injected into the cerebral ventricles. Finally, we observed that the effect of intra-VTA oxytocin to suppress 10% sucrose intake was significantly attenuated by pretreatment with L-368,899, supporting the suggestion that the VTA oxytocin treatment suppresses intake through action at oxytocin receptors. These findings support the suggestion that endogenous oxytocin action within the VTA suppresses sucrose intake. We conclude that oxytocin receptors in the VTA play a physiologic role in the control of sucrose ingestion.
authors.affiliation: Department of Psychology & Program in Neuroscience Florida State University, Box 3064301 Tallahassee, FL 32306-4301, USA.
authors.forename: Kiersten
authors.initials: K
authors.lastname: Mullis
authors.forename: Kristen
authors.initials: K
authors.lastname: Kay
authors.forename: Diana L
authors.initials: DL
authors.lastname: Williams
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001892:Camphanes / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects*; D008297:Male; D010120:Oxytocics / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018045:Receptors, Oxytocin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013395:Sucrose; D017557:Ventral Tegmental Area / Q000187:drug effects*
chemical_list: D001892:Camphanes; D010120:Oxytocics; D010879:Piperazines; D018045:Receptors, Oxytocin; D010121:Oxytocin; D013395:Sucrose; C086206:L 368899
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