Intracerebroventricular (i.c.c.) injections of muscimol (0.03-3 microgram/kg) and GABA (30-1000 microgram/kg) caused dose-related reductions in blood pressure and heart rate of anesthetized cats whereas glycine (30-3000 microgram/kg) was much less effective. I.v. administration of muscimol or GABA had little or no effect. Renal sympathetic nerve discharge was also reduced by central GABA receptor stimulation. The effects of both muscimol and GABA were reversed by either picrotoxin or bicuculline administered intravenously. The results suggest an important role for GABA receptors in the central regulation of blood pressure and heart rate.