Distribution of P2X receptors in the rat adrenal gland

The distribution of each of the seven subtypes of ATP-gated P2X receptors was investigated in the adrenal gland of rat utilizing immunohistochemical techniques with specific polyclonal antibodies to unique peptide sequences of P2X(1-7) receptors. A small number of chromaffin cells showed positive immunoreaction for P2X(5) and P2X(7), with the relative occurrence of P2X(7)-immunoreactive chromaffin cells exceeding that of P2X(5). The preganglionic nerve fibres that form terminal plexuses around some chromaffin cells showed P2X(1) immunoreactivity. Intrinsic adrenal neurones were observed to be positively stained for P2X(2) and P2X(3) receptors. P2X(2) immunoreactivity occurred in several neurones found singly or in groups in the medulla, while only a small number of neurones were immunoreactive for P2X(3). Adrenal cortical cells were positively immunostained for P2X(4-7). Immunoreactivity for P2X(4) was confined to the cells of the zona reticularis, while P2X(5-7) immunoreactivities occurred in cells of the zona fasciculata. The relative occurrence of immunoreactive cortical cells of the zona fasciculata was highest for P2X(6), followed by P2X(7) and then P2X(5). The smooth muscle of some capsular and subcapsular blood vessels showed P2X(2) immunoreactivity. The specific and widespread distribution of P2X receptor subtypes in the adrenal gland suggests a significant role for purine signalling in the physiology of the rat adrenal gland.