Identification of functionally distinct isoforms of the N-type Ca2+ channel in rat sympathetic ganglia and brain.

The N channel is critical for regulating release of neurotransmitter at many synapses, and even subtle differences in its activity would be expected to influence the efficacy of synaptic transmission. Although several splice variants of the N channel are expressed in the mammalian nervous system, their biological importance is presently unclear. Here, we show that variants of the alpha1B subunit of the N channel are expressed in sympathetic ganglia and that alternative splicing within IIIS3-S4 and IVS3-S4 generate kinetically distinct channels. We further show a striking difference between the expression pattern of the S3-S4 variants in brain and peripheral ganglia and conclude that the brain-dominant form of the N channel gates 2-to-4-fold more rapidly than that predominant in ganglia.