Transient expression of P2X(1) receptor subunits of ATP-gated ion channels in the developing rat cochlea.
The expression pattern of the ATP-gated ion channel P2X(1) receptor subunit was studied in the developing rat cochlea by riboprobe in situ hybridisation and immunohistochemistry. Embryonic (E12, E14, E16 and E18) and postnatal (P0, P2, P4, P6, P10 and adult) rat cochleae were examined. Both mRNA and protein localisation techniques demonstrated comparable P2X(1) receptor expression from E16 until P6 but this expression was absent at later developmental stages. P2X(1) receptor mRNA expression was localised within the otic capsule and associated mesenchyme (from E16 to P6), spiral limbus (from P0 to P6) and within the spiral ligament adjacent to the insertion of Reissner's membrane (from P2 to P6). P2X(1) receptor protein had a similar distribution based upon immunoperoxidase localisation. P2X(1) receptor-like immunoreactivity was detected in the otic capsule and the surrounding mesenchyme (from E16 to P6), spiral limbus (from P0) and epithelial cells of Reissner's membrane (from P2 to P6). The spiral ganglion neurones showed the earliest P2X(1) receptor expression (from E16 to P6). This became associated with immunolabelling of their afferent neurite projections to the base of the developing inner and outer hair cells (observed from E18 and peaking at P2). Immunolabelling of the efferent nerve fibres of the intraganglionic spiral bundle (from E18 to P6) within the spiral ganglion was also observed. The results suggest that ATP-gated ion channels assembled from P2X(1) receptor subunits provide a signal transduction pathway for development of afferent and efferent innervation of the sensory hair cells and purinergic influence on cochlear morphogenesis.
Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
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Nikolic
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Housley
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Luo
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Ryan
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Thorne
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation; D003051:Cochlea / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology*; D004848:Epithelium / Q000378:metabolism; D006198:Hair Cells, Auditory / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008648:Mesoderm / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D021122:Protein Subunits; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D058469:Receptors, Purinergic P2X
D007473:Ion Channels; D021122:Protein Subunits; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D000255:Adenosine Triphosphate