DIFFERENTIAL EXPRESSION OF SODIUM-CHANNEL GENES IN RETINAL GANGLION-CELLS

Action potential electrogenesis in the axons of retinal ganglion cells is supported by voltage-gated sodium channels, and a tetrodotoxin (TT X)-inhibitable sodium conductance participates in anoxic injury of the se axons within the optic nerve. However, the subtypes of sodium chann els expressed in retinal ganglion cells have not been identified. In t his study, we used reverse transcription-polymerase chain reaction (RT -PCR) and restriction enzyme mapping, together with in situ hybridizat ion, to examine the expression of transcripts for sodium channel alpha -subunits I, II, III, NaG, Na6, hNE/PN1 and SNS, and beta-subunits 1 a nd 2, in the retina of the adult rat. RT-PCR yielded high levels of am plification of I, II, III, Na6, beta(1) and beta(2) transcripts. In si tu hybridization demonstrated the presence of all these mRNAs in the c ell bodies of retinal ganglion cells. Retinal ganglion cells thus expr ess multiple sodium channel mRNAs, suggesting that they deploy several different types of sodium channels. (C) 1997 Elsevier Science B.V.