Inhibitory action of the ventral noradrenergic bundle on the lateral hypothalamic neurons through alpha-noradrenergic mechanisms in the rat.

Electrical stimulation of the ventral noradrenergic bundle (V-NA bundle) produced 3 types of responses in lateral hypothalamic neurons: IPSPs, a polysynaptic EPSP-IPSP sequence and antidromic spikes. The IPSPs were considered to be monosynaptic due to the fixed latencies seen at stimulus intensities. Iontophoretic application of an alpha-NA antagonist blocked only the presumed monosynaptic inhibition. Most of the glucose-sensitive neurons were inhibited by stimulation of the V-NA bundle. These results may account for the hyperphagia and obesity produced by selective lesions of the V-NA bundle.