P2X(2) RECEPTOR SUBUNIT EXPRESSION IN A SUBPOPULATION OF COCHLEAR TYPE-I SPIRAL GANGLION NEURONS

SPIRAL ganglion neurones in rat cochlea express three different isofor ms of the P2X(2) receptor subunit which assemble into ATP-gated ion ch annels. Two of these P2X(2)R subunit isoforms have previously been det ected in other auditory tissues. The third isoform (designated P2X(2-3 )R) has not been described. This isoform lacks 39 bp immediately prior to the stop codon, corresponding to a 13 amino acid deletion of the e xtreme C-terminus domain. Using direct in situ RT-PCR, expression of P 2X(2)R mRNA was confined to a subpopulation of type I spiral ganglion neurones. This study supports a role for extracellular ATP as a neurot ransmitter for a discrete population of auditory neurones where variat ion in P2X(2)R isoform assembly may confer functional heterogeneity, i ncluding enhanced desensitization.