GABA(A) RECEPTORS IN THE ROSTRAL VENTROLATERAL MEDULLA MEDIATE THE DEPRESSOR RESPONSE INDUCED BY STIMULATION OF THE GREATER SPLANCHNIC NERVE AFFERENT-FIBERS IN RATS

Experiments have been carried out to investigate the chemical substrat e in the rostral ventrolateral medulla (RVLM) underlying the depressor responses induced by activation of the greater splanchnic nerve (GSPL ) afferent fibres of the rat. In anaesthetised rats with urethane and alpha-chloralose, microinjection of bicuculline, a GABAA receptor anta gonist, into the RVLM, attenuated largely the depressor responses elic ited by electrical stimulation of the GSPL afferent fibres, while stry chnine or saline had no effect. In 18 RVLM neurons (including seven id entified cardiovascular neurons), iontophoresis of bicuculline also si gnificantly blocked the inhibition evoked by stimulation of the GSPL a fferent inputs. We suggest that the depressor responses induced by sti mulation of the GSPL afferent fibres involve a GABAA-receptor-mediated mechanism in the RVLM in rats. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.