[Ventrobulbular hypotensive action of muscimol]

Muscimol, a rigid analogue of GABA has been injected in the CNS of urethane anesthetized, normotensive cats. Injected either intracisternally (1 or 2 microgram/kg, 0.05 ml) or directly by microinjection in a restricted ventrolateral region of the brain stem (0.5 or 1 microgram/kg, 0.5 microliter), muscimol induced hypotension and bradycardia. These central cardiovascular effects of muscimol were antagonized by bicuculline, a "specific" GABA antagonist agent. These data emphasize the involvement of gabergic mechanisms in the central cardiovascular control, at least in the ventrolateral part of the medulla oblongata.