Excitatory and inhibitory effects of globus pallidus and substantia nigra on the lateral hypothalamic activity in the rat.

Stimulation of the rat globus pallidus (GP) and substantia nigra (SN), while recording in the lateral hypothalamus, revealed mutual interconnections. Stimulation of GP produced an EPSP-IPSP sequence, while SN stimulation produced EPSP only. Antidromic LH spikes were obtained with either stimulation. Inhibitory interneurons responsible for the IPSP are located in the dorsolateral part of the LH. In the LH, only glucose sensitive neurons were specifically facilitated by SN stimulation and inhibited by GP stimulation. Dopamine and noradrenaline, applied electrophoretically to these neurons, yielded inhibition in a dose response manner, denying the possibility of dopamine as an excitatory transmitter substance. The mutual interrelationship between the LH and other centers, including the frontal cortex, may well influence motivation of feeding and other behavior.