Localization of P2X7 receptor immunoreactivity in the dorsal root ganglia of guinea pig.

The P2X7 receptor mRNA and proteins in guinea-pig dorsal root ganglia (DRG) were studied by using RT-PCR and immunohistochemistry. The co-localization of P2X7 receptor with four cytochemical markers, the neurofilament protein NF200, S100, substance P and isolectin B4 (IB4) binding glyco-conjugates, were also examined. It was found that P2X7 receptor immunoreactivity (P2X7 R-IR) was present mostly in large- and medium-sized DRG neurons (62% +/- 9% and 36% +/- 6% respectively in all P2X7 R-IR neurons). All the P2X7R-IR neurons were also NF200 and S100 immunopositive. However, in a small number of NF200 or S100 immunopositive neurons no P2X7R-IR was detectable. All the IB4-positive or substance P-immunopositive neurons had no P2X7R-IR. These results demonstrate that P2X7 receptors are expressed in a large subpopulation of DRG neurons and they may play a role in the transduction of specific peripheral sensory signals.