Hypothalamic involvement in the locomotor stimulant or satiety action of thyrotropin-releasing hormone and amphetamine.

To determine whether the locomotor stimulant and the anorexic actions of thyrotropin-releasing hormone (TRH) and amphetamine were mediated through the hypothalamic nuclei, rats were infused with either TRH or amphetamine through previously implanted hypothalamic cannulae. Administration of TRH or amphetamine into the ventromedial hypothalamus, but not the lateral hypothalamus and the anterior hypothalamus, caused locomotor stimulation in rats. On the other hand, administration of TRH or amphetamine into the lateral hypothalamus, but not the ventromedial hypothalamus or the anterior hypothalamus, caused a reduction in food consumption without affecting relative water intake (or water-to-food ratio) in the rat. The data indicate that the ventromedial hypothalamus is the most sensitive site of the TRH- or amphetamine-induced locomotor stimulation and the action of TRH or amphetamine on the lateral hypothalamus is also a possible mechanism mediating anorexia.