MEDIATION OF THE CARDIOVASCULAR-RESPONSE OF ADENOSINE A(1) RECEPTOR THROUGH A GABA(B) RECEPTOR IN THE SPINAL-CORD OF THE RAT

Cardiovascular inhibitory effects induced by intrathecal (i.t.) admini stration of adenosine A(1) receptor agonist and its modulation by cycl ic AMP was suggested by our previous report. In this experiment, we ex amined the mediation of cardiovascular effects of adenosine A(1) recep tor by gamma-aminobutyric acid receptors A and B (GABA(A) and GABA(B)) in the spinal cord. I.t. administration of 10 nmol of N-6-cyclohexyla denosine (CHA), an adenosine A(1) receptor agonist, and pretreatment w ith bicuculline (10 nmol, i.t), a GABA(A) receptor antagonist, and 5-a minovaleric acid (50 nmol, i.t.), a GABA(B) receptor antagonist, prior to injection of CHA were performed in anesthetized, artificially vent ilated Sprague-Dawley rats. I.t. injection of 50 nmol of 5-aminovaleri c acid significantly attenuated the inhibitory cardiovascular effects of CHA but 10 nmol of bicuculline did not alter CHA-induced cardiovasc ular actions. It is suggested that cardiovascular responses of adenosi ne A(1) receptor is meditated by GABA(B) receptor in the spinal cord. (C) 1998 Published by Elsevier Science Ireland Ltd.