Glycine receptor regulation of neurokinin1 receptor function in rat dorsal horn neurones.

Activation of spinal neurokinin1 (NK1) receptors leads to increases in the extracellular concentration of glycine in the dorsal horn. We have investigated the role of the inhibitory glycine receptor as a regulator of NK1 receptor-mediated effects on dorsal horn neurones. Ionophoretic application of GR82334, a selective NK1 antagonist, did not alter dorsal horn neuronal activity evoked by cutaneous applications of mustard oil. However, in the presence of the glycine antagonists, strychnine or phenylbenzene-omega-phosphono-alpha-amino acid (PMBA), GR82334 displayed inhibitory properties. Therefore inhibitory glycine receptors may mask the contribution made by NK1 receptors to nociceptive processing. This is discussed with reference to the role of NK1 receptors during brief and long duration nociceptive transmission.