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Transient expression of P2X(1) receptor subunits of ATP-gated ion channels in the developing rat cochlea
P Nikolic1, G D Housley, L Luo
1Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
Insights
The study reveals that the ATP-gated ion channel P2X(1) receptor subunit is expressed in the developing rat cochlea, particularly in sensory neurons and nerve fibers. This expression is crucial for the development of auditory hair cell innervation and cochlear structure.
Area of Science:
- Neuroscience
- Developmental Biology
- Otolaryngology
Background:
- The cochlea's development involves complex cellular interactions and signaling pathways.
- ATP-gated ion channels, such as the P2X(1) receptor, are implicated in various developmental processes.
Purpose of the Study:
- To investigate the expression pattern of the P2X(1) receptor subunit in the developing rat cochlea.
- To understand the role of P2X(1) receptors in cochlear innervation and morphogenesis.
Main Methods:
- Riboprobe in situ hybridization and immunohistochemistry were used to localize P2X(1) receptor mRNA and protein.
- Rat cochleae were examined at various embryonic and postnatal developmental stages.
Main Results:
- P2X(1) receptor expression was detected from embryonic day 16 (E16) to postnatal day 6 (P6), and absent later.
- Expression was observed in the otic capsule, mesenchyme, spiral limbus, Reissner's membrane, and spiral ganglion neurons.
- Afferent and efferent nerve fibers innervating hair cells showed P2X(1) receptor immunoreactivity.
Conclusions:
- P2X(1) receptor subunits contribute to ATP-gated ion channel signaling in the developing cochlea.
- These channels play a role in the development of afferent and efferent innervation of hair cells.
- Purinergic signaling via P2X(1) receptors influences cochlear morphogenesis.
Abstract:
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.
