GABA-B RECEPTOR-MEDIATED INHIBITION OF FORSKOLIN-STIMULATED CYCLIC-AMP ACCUMULATION IN RAT SPINAL-CORD

GABA (30-1000 muM) and the GABA(B) agonist, (-)baclofen (10-100 muM), but not (+)baclofen, inhibited forskolin-induced cAMP formation in rat spinal cord slices. In contrast, GABA and (-)baclofen failed to enhan ce the stimulation of cAMP induced by noradrenaline in the same tissue , even though they both increased the response to noradrenaline in cer ebral cortex slices. Neonatal capsaicin treatment, which reduces the d ensity of GABA(B) binding sites in the cord, did not modify the effect of GABA or (-)baclofen on the forskolin-induced elevation of cAMP. (- )Baclofen and GABA inhibition of forskolin effects were insensitive to the GABA(B) antagonists CGP 35348 and CGP 36742 in the spinal cord. S ince CGP 35348 antagonizes baclofen-induced antinociception, it seems unlikely that this effect stems from any change in cAMP within the spi nal cord.