Fig. 4.

Localization of P2X₂ receptor expression in the cochlear partition and assessment of ATP-gated conductances. (A) P2X₂ receptor immunofluorescence. Note the strong signal in WT cochlea, on Reissner’s membrane epithelial cells (RM), spiral limbus (sl), and organ of Corti (o/C), including the inner and outer hair cells (IHCs and OHCs, respectively) (pseudocolored projection of confocal image stack of immunofluorescence from a 50-µm cryosection; 3-mo-old mouse). sm, scala media; stv, stria vascularis; sv, scala vestibuli. (Right) Unprocessed immunofluorescence images for WT and P2RX2-null tissue (KO). (B) Examples of whole-cell voltage-clamp recordings from RM, IHC, and OHC. Records from cells isolated from KO and WT tissue are overlaid. Bars indicate the 5-s applications of 100 µM ATP at a holding potential of −60 mV. (C) Average ATP-induced current responses from RM, IHC, and OHC from WT cochleae, compared with no responses in cells from P2RX2-null mice. (D) Microinjection of ATP (0.1 and 1 mM, 10 nL) into scala media produced a dose-dependent reduction in EP in WT mice that was absent in P2RX2-null mice. bl, baseline. (E) Associated dose-dependent reduction in CoPR produced by ATP in WT mice. There was no change in CoPR in P2RX2-null mice. ***P < 0.001.