TRH increases locomotor activity in rats after injection into the hypothalamus.

Thyrotropin releasing hormone (TRH) had been reported to increase locomotor activity in rats and mice. In an attempt to localize this phenomenon, TRH (1 microgram, bilateral) was injected into the caudate nucleus, septum and hypothalamus of rats. Locomotor activity increased after injection of TRH into the hypothalamus, but not into the other two sites. These data may indicate that increased locomotor activity is elicitable by TRH only in sharply delimited sites in the nervous system.