A T-type calcium channel from mouse brain

A member of the low-voltage-activated calcium channel family was identified in mouse brain by taking advantage of amino acid sequences that have been evolutionary conserved. The identified sequence is similar to that of the recently cloned rat alpha(1G) T-type calcium channel, but there are differences in two insertions in the intracellular connecting loops. Northern blot analysis indicates that its expression is strong in the brain. In situ hybridization revealed that, in mouse brain, the alpha(1G) mRNA is found in the cerebellum, hippocampus, thalamus and olfactory bulb. In contrast to L-type calcium channel currents, I-Ba and I-Ca through the alpha(1G) channel expressed in HEK293 cells did not differ in terms of current density, voltage dependence of current activation, inactivation and deactivation, and speed of recovery from voltage-dependent inactivation. The kinetics of I-Ca inactivation were significantly slower than those of I-Ba. The expressed alpha(1G) channel has a relatively high sensitivity to mibefradil, but is only slightly affected by Ni2+.