ATP P2XReceptors Mediate Fast Synaptic Transmission in the Dorsal Horn of the Rat Spinal Cord

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Abstract
ATP has been proposed to mediate synaptic transmission in the spinal cord dorsal horn, particularly in the pathway carrying nociceptive information. Using transverse spinal cord slices from postnatal rats, we show that EPSCs mediated by P2Xreceptors, and presumably activated by synaptically released ATP, are evoked in a subpopulation of spinal cord lamina II neurons, a region known to receive strong input from nociceptive primary afferents. The P2X receptors on acutely dissociated dorsal horn neurons are nondesensitizing, insensitive to αβ methylene ATP, and show strong but variable sensitivity to the antagonists suramin and pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS). These characteristics are consistent with a heterogeneous population of P2X receptors, the composition of which includes P2X2, P2X4, and P2X6receptor subtypes. Our results suggest that ATP-activated P2X receptors in lamina II of the rat spinal cord may play a role in transmitting or modulating nociceptive information.