Influence of oxytocin on feeding behavior in the rat.

Oxytocin, whether administered intraperitoneally (IP) (375-6,000 micrograms/kg) or intracerebroventricularly (ICV) (1-10 micrograms/rat), dose-dependently reduced food consumption and time spent eating and increased the latency to the first meal in rats fasted for 21 hr. Pretreatment with the oxytocin antagonist d(CH2)5Tyr(Me)-[Orn8]vasotocin (ICV 10 micrograms/rat) completely prevented the feeding inhibitory effect of an equal dose of ICV oxytocin, and per se increased food intake. Our data further support the hypothesis that oxytocin plays the role of neurotransmitter or neuromodulator in the CNS, and suggest that its involvement in a number of homeostatic systems may include appetite control.