Effect of intracerebroventricular administration of the GABAB-receptor agonist baclofen on operant feeding in satiated pigs.

1. The present study investigated the effects of intracerebroventricular (i.c.v.) administration of the GABAB-receptor agonist baclofen on food and water intake in satiated pigs previously trained to make operant responses for food and water, which were available ad libitum. 2. Baclofen (25-100 nmol) i.c.v. produced a dose-related increase in food intake. Baclofen (50 nmol) increased feeding during the first 15 min after administration (P less than 0.01), while the 100 nmol dose increased feeding during the first 30 min (P less than 0.01). None of these doses of baclofen had any affect on the daily (24 h) food intake. 3. The effect of baclofen (50 nmol) on feeding was prevented by pretreating the animals with the GABAB antagonist phaclofen (500 nmol, i.c.v.). 4. Baclofen (25-100 nmol) i.c.v. had no significant effects on water intake. 5. Intravenous administration of baclofen (100 nmol) had no effect on food intake, thus eliminating the possibility that i.c.v. baclofen might have stimulated feeding by a peripheral mode of action. 6. These results show that baclofen increases food intake in satiated pigs, and that this effect is mediated by the drug acting at central GABAB-receptors.