Physiological Maturation of Photoreceptors Depends on the Voltage-Gated Sodium Channel NaV1.6 (Scn8a)

• Published in: The Journal of neuroscience 2005-05, Vol.25 (20), p.5046-5050
• Main Authors: Cote, Patrice D, De Repentigny, Yves, Coupland, Stuart G, Schwab, Yannick, Roux, Michel J, Levinson, S. Rock, Kothary, Rashmi
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Brief Communications; Dose-Response Relationship, Radiation; Electroretinography - methods; Gene Expression Regulation, Developmental - genetics; Gene Expression Regulation, Developmental - physiology; Life Sciences; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Electron, Transmission - methods; NAV1.6 Voltage-Gated Sodium Channel; Nerve Tissue Proteins - deficiency; Nerve Tissue Proteins - physiology; Neurons and Cognition; Photic Stimulation - methods; Photoreceptor Cells - growth & development; Photoreceptor Cells - physiology; Photoreceptor Cells - radiation effects; Photoreceptor Cells - ultrastructure; Sodium Channels - deficiency; Sodium Channels - physiology
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/JNEUROSCI.4692-04.2005

Voltage-gated sodium channels (VGSCs) ensure the saltatory propagation of action potentials along axons by acting as signal amplifiers at the nodes of Ranvier. In the retina, activity mediated by VGSCs is important for the refinement of the retinotectal map. Here, we conducted a full-field electroretinogram (ERG) study on mice null for the sodium channel NaV1.6. Interestingly, the light-activated hyperpolarization of photoreceptor cells (the a-wave) and the major "downstream" components of the ERG, the b-wave and the oscillatory potentials, are markedly reduced and delayed in these mice. The functional deficit was not associated with any morphological abnormality. We demonstrate that Scn8a is expressed in the ganglion and inner nuclear layers and at low levels in the outer nuclear layer beginning shortly before the observed ERG deficit. Together, our data reveal a previously unappreciated role for VGSCs in the physiological maturation of photoreceptors.