Variants of the Drosophila melanogaster Ih-channel are generated by different splicing

Functional expression of one of the DMIH variants with a long N-terminus in HEK293 cells produced unitary currents that were preferentially selective for potassium over sodium ions and were activated by hyperpolarizing voltage steps. Cyclic nucleotides shifted the voltage activation curve to more positive membrane potentials. The current kinetics and modulatory influence of cyclic nucleotides resemble closely those of other invertebrate Ih-channels, but activation by hyperpolarizing voltage steps had a V1/2 of 123 mV, a more negative value than those of other recombinantly expressed insect Ih-channels with a short N-terminus.