VOLTAGE-GATED POTASSIUM CHANNELS OF SCHWANN-CELLS FROM TROUT LATERAL-LINE NERVE - A COMBINED ELECTROPHYSIOLOGICAL AND MOLECULAR CHARACTERIZATION

Voltage-gated ionic currents were recorded from explant cultured and f reshly dissociated SC from trout lateral line nerve using the whole-ce ll configuration of the patch clamp technique. In the majority of case s a delayed rectifier potassium outward current (KD) was found exclusi vely, which activated at potentials greater than or equal to -40 mV an d reached maximal amplitudes of 240 +/- 25.2 nA at 60 mV testpulse pot ential. This current showed no voltage-dependent kinetics of inactivat ion and was insensitive to TEA but was effectively blocked by 4-AP. By single cell RT-PCR the transcript of a shaker-related potassium chann el gene, termed tsha1 (a fish homologue of Kv1.2), was selectively amp lified. In its biophysical and pharmacological properties the native w hole cell potassium outward current of trout Schwann cells closely mat ched those of the cloned tsha1 subunit previously expressed in xenopus oocytes. A small subpopulation of freshly dissociated SC (less than 1 0%) at hyperpolarizing potentials elicited a potassium inward current instead, which in its kinetics closely resembled the inward rectifier (K-IR) Of mammalian SC. Neither voltage-gated sodium currents nor memb rane currents activated by excitatory amino acids (glutamate, kainate, and quisqualate) were observed. (C) 1998 Wiley-Liss, Inc.