Abstract
The ventral pallidum (VP) is suggested to control feeding behavior. The functions of the ventral pallidum are considered to be modulated by GABAergic projection from the nucleus accumbens. Previous studies have shown that blockade of GABA receptors in the VP increased food intake. Our previous study has also demonstrated that lesions of the VP decreased the intake of palatable sucrose solution. However, it is unclear whether GABA is critically involved in the ingestion of palatable taste stimuli. To address this issue, we examined the effects of pharmacological manipulations of GABAergic, dopaminergic, glutamatergic, or opioidergic neurotransmission within the VP on the intake of taste solutions in rats. Injection of bicuculline, a GABAA receptor antagonist, into the VP significantly increased the intake of sweet solution, but not distilled water and bitter solution. On the contrary, injection of muscimol, a GABAA receptor agonist, into the VP resulted in intensive aversive reactions to sweet solution and distilled water. Although solution intakes were not significantly changed by injection of dopamine or glutamate antagonist, saccharin intake tended to decrease by injection of both antagonists. Injection of [D-Ala(2), NMe-Phe(4), Gly-ol(5)]-enkephalin (DAMGO), a μ-selective opioid agonist, increased palatable sucrose intake. These results suggest that the GABAergic, but not dopaminergic and glutamatergic, transmission in the VP critically modulated the intake of palatable solution. [Jpn J Physiol 55 Suppl:S200 (2005)]
