Intracranial alpha-methyl-P-tyrosine and response for electrical brain stimulation.

Chemitrodes, allowing electrical stimulation of the brain at the same site, were implanted in 18 rats aimed at the medial forebrain bundle of the lateral hypothalamus. After these animals were trained to bar-press for electrical brain stimulation, the crystalline form of alpha-methyl-paratyrosine (AMPT), an inhibitor of catecholamine synthesis, was administered intracranially, and change in response rate was noted. Intracranial tyrosine administration was also tested as a control study. It was found that AMPT depressed rate of response of intracranial self-stimulation, whereas tyrosine administered intracranially exhibited no such effects. This result lends support to data reported in the literature on the use of AMPT administered intraperitoneally or orally, and suggests a noradrenergic or dopaminergic system of reward in the lateral hypothalamus.