P2 receptors in cerebellar neurons: Molecular diversity of ionotropic ATP receptors in Purkinje cells

ATP is now recognized as a fast neurotransmitter after the demonstration of synaptic transmission mediated by ATP in the medial habenula, locus coerul eus, spinal cord, and hippocampus. We focused on the postnatal rat cerebell um as a model territory and studied the role of ATP neurotransmission using cultured cells. Cerebellar Purkinje neurons in culture express ionotropic P2X receptors. We have shown that Ca2+ signals mediated by ATP in Purkinje cells present pharmacological profile characteristics of ATP receptors form ed by P2X(2) subunits. However, the complete range of known P2X subunits ar e expressed in the cerebellum. With the aid of the RT-PCR technique we iden tified mRNA for P2X(1-4) and P2X(6) subunits in the rat cerebellum during t he first postnatal week. These results have been confirmed by Southern blot ting of PCR products using selective P2X probes. This opens the question of the relative contribution of each subunit to functional channels. Immunocy tochemical labeling using anti-P2X antibodies reveal that several P2X subun its colocalize to the same Purkinje cell. This raises the possibility of ex tensive hetero-oligomerization of P2X subunits. Patch-clamping of Purkinje cells in culture indicates the presence of two subpopulations of ATP recept ors: a fast and rapidly desensitizing receptor and a nondesensitizing recep tor with slower kinetics. Our results suggest that both receptors may be fo rmed by co-assembly of dissimilar P2X subunits. Drug Dev. Res. 52:104-113, 2001. (C) 2001 Wiley-Liss, Inc.