Effects of intraventricular injections of gamma-aminobutyric acid and related substances on feeding behavior in satiated sheep.

Feed intake was measured following injections of gamma-aminobutyric acid (GABA), muscimol (a GABA agonist), and picrotoxin (a GABA antagonist) into the lateral ventricles of satiated sheep. Doses ranging from 0.20 to 3200 nmol of GABA did not affect feeding behavior at 15, 30, 60, and 120 min postinjection. A dose of 160 nmol of muscimol induced a marked increase in feeding, comparable to that provoked by an injection of 78 mumol of pentobarbital. Muscimol-induced feeding was blocked effectively by a preinjection of picrotoxin. These observations implicate that neurons sensitive to gamma-aminobutyric acid may be involved in the control of feeding behavior in ruminants.