Some physiological and pharmacological properties of slow depolarization of substantia gelatinosa neurons by repetitive stimulation of C-fibers of dorsal root in adult rat spinal cord slices with dorsal root attached

Transverse slices of the spinal cord with dorsal root attached were prepare d from adult rats and used to record the response of the spinal substantia gelatinosa neurons evoked by repetitive stimulation of the dorsal root with a whole cell patch clamp method. The repetitive stimulation of 10 trains ( 20 pulses at 100 Hz/train) with an intensity necessary to activate C-fibers , but not A-fibers alone, evoked slow depolarization (SD) during it and the SD disappeared within 1 min after the termination of it. The SD was comple tely inhibited by 500 nM of tetrodotoxin (TTX), but not significantly chang ed by 50 nM of TTX, nor 20 mu M CNQX + 50 mu M AP5, nor 1 mu M CP-99994. DA MGO inhibited the SD in a concentration dependent manner (10 nM-1 mu M), bu t 1 mu M DPDPE and 1 mu M U-50488H did not. The inhibitory effect of DAMGO (1 mu M) was reversed by naloxone (1 mu M). These results suggest that the SD of substantia gelatinosa neurons evoked by repetitive stimulation of C-f ibers of the dorsal root is an event relevant to nociception in the spinal dorsal horn. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.