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J. Qu, L. Chen, I. Mulo, K. Myhr; The Development of Potassium Channels in Mouse Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5970.
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© ARVO (1962-2015); The Authors (2016-present)
The development of excitability in retinal ganglion cells is critical for adult ganglion cell function, and for transmitting activity that is critical for refinements of ganglion cell axonal terminals during development. This project focused on the development of two potassium channels that can regulate intrinsic excitability. The first was Kv4.2, which mediates the fast transient potassium current (IA). The second, SK2, mediates the apamin-sensitive small-conductance calcium-activated potassium current (ISK) underlying afterhyperpolarization. This project determined the differential distributions of Kv4.2 and SK2 in the retina through postnatal mouse development.
Immunohistochemistry of Kv4.2 and SK2 in retinas from postnatal day 4 (P4) to P42 were studied in wholemounts and slices. Kv4.2 and SK2 immunoreactivities were measured by standard fluorescence and confocal microscopy.
Kv4.2 immunoreactivity (Kv4.2-IR) was absent at P4, appeared by P13 and persisted through P42. Once expressed, Kv4.2-IR appeared in two distinct bands in the inner plexiform layer as well as in somas and primary dendrites of a small proportion of ganglion cells. SK2-IR was already present in the ganglion cell layer at P4. During the second postnatal week, SK2-IR was refined to a small proportion of somas in the ganglion cell layer and inner nuclear layer. Strong SK2-IR also appeared in the inner plexiform layer. This expression pattern persisted through P42.
Kv4.2 is expressed in a subset of retinal ganglion cells, probably one or a few functional subtypes, based on the restriction of Kv4.2-IR to specific substrata of the inner plexiform layer. This expression increases with development, correlating with the increase of IA in a subset of ganglion cells. Similarly, SK2 is restricted to a subset of ganglion cells during postnatal development, although its expression appears earlier and is more widespread than that of Kv4.2.
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