Synergistic effects of dopamine agonists and centrally administered neurotensin on feeding.

Several lines of evidence indicate that neurotensin may modulate the activity of dopamine systems in the central nervous system. The present study investigated the possibility that intraperitoneal injections of the dopamine agonists l-dopa and bromocriptine would alter the aphagia produced by central administration of neurotensin. It was found that neurotensin suppressed feeding in food-deprived rats when injected into the lateral ventricle or the ventromedial hypothalamus. Food intake was not affected, however, when the peptide was placed in the lateral hypothalamus. A dose-dependent aphagia was also observed following peripheral injections of l-dopa and bromocriptine. Additionally, the anorectic effect of centrally administered neurotensin was potentiated by concurrent administration of doses of l-dopa or bromocriptine which, when given alone, had no effect on food intake. The data suggest that neurotensin aphagia may be mediated by the peptide's ability to increase the activity of dopamine systems in the central nervous system.