ARE THERE FUNCTIONAL P2X RECEPTORS ON CELL-BODIES IN INTACT DORSAL-ROOT GANGLIA OF RATS

P2X purinoceptors have been suggested to participate in transduction o f painful stimuli in nociceptive neurons. In the current experiments, ATP (1-10 mM), alpha,beta-methylene-ATP (10-30 mu M) and capsaicin (10 nM-1 mu M) were applied to neurons impaled with high resistance micro electrodes in rat dorsal root ganglia (L4 and L5) isolated in vitro to gether with the sciatic nerve and dorsal roots. The agonists were eith er bath applied or focally applied using a picospritzer. GABA (100 mu M) and 40-80 mM K+ solutions gave brisk responses when applied by eith er technique. Only three of 22 neurons with slowly conducting axons (C cells) showed evidence of P2X-purinoceptor-mediated responses. Only t wo of 13 cells which responded to capsaicin (putative nociceptors), an d none of 29 cells with rapidly conducting axons (A cells), responded to the purinergic agonists. When acutely dissociated dorsal root gangl ion cells were studied using patch-clamp techniques, all but four of 3 0 cells of all sizes responded with an inward current to either ATP or alpha,beta-methylene-ATP (both 100 mu M).Our data suggest that few se nsory cell bodies in intact dorsal root ganglia express functional pur inoceptors. (C) 1998 IBRO. Published by Elsevier Science Ltd.