Regional distribution of [35S]2′-deoxy 5′-O-(1-thio) ATP binding sites and the P2Y1 messenger RNA within the chick brain

The distribution of the P2Y(1) receptor protein and transcript in the one-day-old chick brain were determined by quantitative in vitro ligand autoradiography and in situ hybridization histochemistry. We have previously used [S-35]2'-deoxy 5'-O-(1-thio) ATP as a radioligand for the recombinant P2Y(1) receptor transiently expressed in COS-7 cells and have also shown that such sites are present al high density (B-max: similar to 37 pmol radioligand bound/mg protein) in chick brain membranes. Here we report the macroscopic localization of these [S-35]2'-deoxy 5'-O-(1-thio) ATP binding sites within the chick brain. They were found to be widely distributed there (within the range of 0.047 +/- 0.012 to 0.309 +/- 0.035 pmol bound/mg wet tissue). The affinities of P-2 agonists and antagonists at these binding sites was comparable to that found previously for the recombinant P2Y(1) receptor. In parallel experiments, the regional and cellular localization of the P2Y(1) receptor messenger RNA was examined by ia situ hybridization. The transcript was also found to be widely distributed throughout the brain. High levels of hybridization were detected in the cortex piriformis, ectostriatum, hippocampus, cerebellum and in a range of discrete nuclei throughout the brain, including the ovoidalis, isthmo-opticus and spiriformis lateralis nuclei. Localization at cellular level indicates that this receptor transcript is expressed in neurons and also at non-neuronal sites. Furthermore, the distribution of the P2Y(1) transcript and the [S-35]2'-deoxy 5'-O-(1-thio) ATP binding sites matched in a number of the regions and structures mentioned above. The present study clarifies the anatomical distribution of the P2Y(1) receptor within the chick brain. Its broad distribution coupled with its neuronal expression suggest an important role for for this type of metabotropic nucleotide receptor within the brain. (C) 1998 IBRO. Published by Elsevier Science Ltd.