Voltage-gated potassium channels in retinal ganglion cells of trout: a combined biophysical, pharmacological, and single-cell RT-PCR approach.

Retinal ganglion cells of young mature trout were acutely isolated by tissue printing and analyzed with the whole-cell mode of the patch-clamp technique in combination with single-cell RT-PCR. All cells either exhibited spontaneous spiking activity or could be induced to fire trains of action potentials by current injection. Depolarizing voltage steps elicited a TTX-sensitive sodium inward current and a complex outward current that could be subdivided into a calcium-dependent component that was sensitive to 100 nM iberiotoxin as well as three major types of voltage-sensitive currents: 1) a high-threshold (-20 mV) noninactivating current that was highly sensitive to submicromolar TEA and quinine, resembling recombinant mammalian Kv3.1 channels; 2) a low-threshold DTX-sensitive current, matching mammalian Kv1; and 3) a fast-inactivating transient current that was highly sensitive to TEA (3 mM) but resistant to alpha-DTX (1 microM) and quinine (0.1 mM). By multiplex single-cell RT-PCR, coexpression of multiple transcripts encoding Shaker-related channel genes of trout (termed Tsha1-Tsha4) as well as two Shaw-related channels (termed Traw1 and Traw2) could be demonstrated in individual cells. Copyright 2000 Wiley-Liss, Inc.