Adenosine suppresses the response of neurons to gaba in the superficial laminae of the rat spinal dorsal horn.

With the nystatin-perforated whole-cell patch-clamp recording technique, the modulatory effects of adenosine on GABA-activated whole-cell currents were investigated in neurons acutely dissociated from the superficial laminae (laminae I and II) of the rat spinal dorsal horn. The results showed that: (1) GABA acted on GABA(A) receptor and elicited inward Cl(-) currents (I(GABA)) at a holding potential (V(H)) of -40 mV; (2) adenosine suppressed GABA-induced Cl(-) current with affecting neither the reversal potential of I(GABA) nor the apparent affinity of GABA to its receptor; (3) N6-cyclo-hexyladenosine, a selective A(1) adenosine receptor agonist, mimicked the suppressing effect of adenosine on I(GABA), whereas 8-cyclopentyl-1,3-dipropylxanthine, a selective A(1) adenosine receptor antagonist, blocked the suppressing effect of adenosine; (4) chelerythrine, an inhibitor of protein kinase C, reduced the suppressing effect of adenosine on I(GABA); (5) pretreatment with 1,2-bis-(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxy-methyl) ester, a Ca(2+) chelator, did not affect adenosine-induced suppression of I(GABA). The results indicate that: (1) the suppression of adenosine on I(GABA) is mediated by adenosine A(1) receptor and through a Ca(2+)-independent protein kinase C transduction pathway; (2) the interactions between adenosine and GABA might be involved in the modulation of nociceptive information transmission at spinal cord level.