DIFFERENTIAL DISTRIBUTION OF 2 ATP-GATED ION CHANNELS (P-2X RECEPTORS) DETERMINED BY IMMUNOCYTOCHEMISTRY

Several P-2X receptor subunits were recently cloned; of these, one was cloned from the rat vas deferens (P-2X1) and another from pheochromoc ytoma (PC12) cells differentiated with nerve growth factor (P-2X2) Pep tides corresponding to the C-terminal portions of the predicted recept or proteins (P-2X1 391-399 and P-2X2 460-472) were used to generate an tisera in rabbits. The specificities of antisera were determined by st aining human embryonic kidney cells stably transfected with either P-2 X1 or P-2X2 receptors and by absorption controls with the cognate pept ides, In the vas deferens and the ileal submucosa, P-2X1 immunoreactiv ity (ir) was restricted to smooth muscle, whereas P-2X2-ir was restric ted to neurons and their processes, Chromaffin cells of the adrenal me dulla and PC12 cells contained both P-2X1- and P-2X2-ir P-2X1-ir was a lso found in smooth muscle cells of the bladder, cardiac myocytes, and nerve fibers and terminals in the superficial dorsal horn of the spin al cord. In contrast, P-2X2-ir was observed in scattered cells of the anterior pituitary, neurons in the hypothalamic arcuate and paraventri cular nuclei, and catecholaminergic neurons in the olfactory bulb, the substantia nigra, ventral tegmental area, and locus coeruleus, A plex us of nerve fibers and terminals in the nucleus of the solitary tract contained P-2X2-ir. This staining disappeared after nodose ganglionect omy, consistent with a presynaptic function. The location of the P-2X1 subunit in smooth muscle is consistent with its role as a postjunctio nal receptor in autonomic transmission, while in neurons, these recept ors appear in both postsynaptic and presynaptic locations.