Expression of the P2X7 receptor subunit of the adenosine 5'-triphosphate-gated ion channel in the developing and adult rat cochlea.

ATP-gated ion channels assembled from P2X(7) subunits have been implicated in ontogeny and cellular pathology. Here, the expression of the P2X(7) receptor subunit was studied in the embryonic (E14-E18 days) and postnatal (P0-adult) rat cochlea using immunohistochemistry. Strong P2X(7) immunolabelling was observed in the primary auditory neurons of the spiral ganglion from E18 to adult and in the fibres innervating the sensory inner and outer hair cells from birth to adult. Strong immunolabelling of P2X(7) receptor protein was also observed in the inner and outer hair cells over a limited developmental period, from birth to P6. Weak expression was observed in cochlear duct epithelium on E18 and in the supporting cells (footplates of pillar cells in adult and in Böttcher's cells after birth). The immunolocalisation of P2X(7) receptors further implicates extracellular ATP in signalling process in cochlear ontogeny and in establishment and function of auditory neurotransmission. The P2X(7) receptors may be involved in signal transduction and modulation as well as in regulating cell death during development and in pathological conditions. Copyright 2003 S. Karger AG, Basel