Localization of P2X and P2Y receptors in dorsal root ganglia of the cat

The distribution of P2X and P2Y receptor subtypes in upper lumbosacral cat dorsal root ganglia (DRG) has been investigated using immunohistochemistry. Intensity of immunoreactivity for six P2X receptors (P2X(5) receptors were immuno-negative) and the three P2Y receptors examined in cat DRG was in the order of P2Y(2) = P2y(4)> P2X(3)> P2X(2) = P2X(7)> P2X(6)> P2X(1) = P2X(4)> P2Y(1). P2X(3), P2Y(2), and P2Y(4) receptor polyclonal antibodies stained 33.8%, 35.3%, and 47.6% of DRG neurons, respectively. Most P2Y(2), P2X(1), P2X(3), P2X(4), and P2X(6) receptor staining was detected in small- and medium-diameter neurons. However, P2Y(4), P2X(2), and P2X(7) staining was present in large- and small-diameter neurons. Double-labeling immunohistochemistry showed that 90.8%, 32.1%, and 2.4% of P2X(3) receptorpositive neurons coexpressed IB4, CGRP, and NF200, respectively; whereas 67.4%, 41.3%, and 39.1% of P2Y(4) receptor-positive neurons coexpressed IB4, CGRP, and NF200, respectively. A total of 18.8%, 16.6%, and 63.5% of P2Y(2) receptor-positive neurons also stained for IB4, CGRP, and NF200, respectively. Only 30% of DRG neurons in cat were P2X(3)-immunoreactive compared with 90% in rat and in mouse. A further difference was the low expression of P2Y(1) receptors in cat DRG neurons compared with more than 80% of the neurons in rat. Many small-diameter neurons were NF200-positive in cat, again differing from rat and mouse.