IMMUNOHISTOCHEMICAL STUDY OF THE P2X(2) AND P2X(3) RECEPTOR SUBUNITS IN RAT AND MONKEY SENSORY NEURONS AND THEIR CENTRAL TERMINALS

Of the cloned P2X receptor subunits, six are expressed in sensory neur ons, suggesting that the native channels may be heteromultimers with d iverse composition. It has been proposed that P2X(2) and P2X(3) form h eteromultimers in sensory neurons. We further tested this hypothesis b y examining the relationship of P2X(2) and P2X(3) immunocytochemically . In rat dorsal root and nodose ganglia, P2X(2)- and P2X(3)-immunoreac tivity (-ir) were highly colocalized, although single-labeled cells we re also present. In dorsal. root ganglia (DRG), in some cases P2X(2)-i r appeared to be present in satellite cells. In dorsal horn of spinal cord, at low magnification the laminar localization of P2X(2)- and P2X (3)-ir overlapped, but at high magnification colocalization was rarely observed. In contrast, in the solitary tract and its nucleus (NTS), c olocalization of P2X(2)- and P2X(3)-ir was seen at low and high magnif ication. These results suggest that the relationship of P2X(2)- and P2 X(3)-ir is different in nodose and dorsal root ganglia and might refle ct differences in the targeting of P2X receptors in different sensory neurons. In monkey, P2X(2)-ir was observed in DRG neurons and satellit e cells and in dorsal horn of spinal cord. P2X(3)-ir was also seen in DRG neurons. However, the presence of P2X(2)-ir in NTS as well as the presence of P2X(3)-ir in spinal cord and NTS could not be established definitively. These results suggest species differences, although a mo re extensive study of primate sensory systems is necessary. (C) 1997 P ublished by Elsevier Science Ltd.