Abstract
Our previous study has demonstrated that excitation of neurons in the rat ventromedial hypothalamus (VMH) induced running behavior. In this study we examine the effect of neuropeptide oxytocin injection into the VMH on the running behavior. Microinjection of oxytocin into the VMH induced a dose-dependent increase in the running behavior in male rats. On the other hand, simultaneous injection of oxytocin receptor antagonist, d(CH2)5-Tyr(Me)2-Orn8-Vasotocin, with oxytocin inhibited the running behavior. Oxytocin administration into the VMH of ovariectomized (OVX) female rats also induced running behavior. In the estrogen-treated OVX rats oxytocin injection into the VMH further increased the running behavior than OVX rats. In the histological study, effective cites of oxytocin injection on inducing running behavior is located in the ventro-lateral part of the VMH. These findings suggest that oxytocin receptor in the VMH is involved in the induction of the running behavior, and in female rats estrogen facilitate the effect of oxytocin on running behavior. [J Physiol Sci. 2006;56 Suppl:S207]
