Fig. 3. Analysis of P2X receptor expression in neonatal rat SGN. (A) Isolation of a single SGN from a P4 rat cochlear slice using a micropipette. (B) Example of an inward current response to the P2X₃ and P2X_2/3 receptor agonist ,ßMeATP (100 µM) in a SGN using whole-cell voltage clamp (holding potential -60 mV). (C) Block of the ATP response (100 µM, 5 seconds of focal application) by the P2X_2/3 receptor-specific antagonist A-317491 (500 nM, bath superfusion). (D) Real-time PCR amplification plot showing detection of P2X₃ cDNA in a sample of individual SGN. (E) Average transcript copy number for each P2X receptor subunit and the housekeeping genes Nse and Gapdh in individual neurons. Note that the P2X₃ transcript number was twice that of P2X₂ (^*P<0.01; P2X₃ transcript number was significantly greater than the other P2X subunits; GAPDH transcript copy number was significantly greater than NSE transcript copy number). (F) Relative distribution of P2X receptor subunits in the population of SGN. This plot shows the normalized mRNA transcript copy number for each of the seven candidate P2X receptor subunits expressed by individual SGN. (G) Immunofluorescence labeling of P2X₂, P2X₃ and P2X₄ in neonatal (P4) spiral ganglion tissue.