Calcium Channels in the Mammalian Brain

Calcium channels occupy a unique position in the economy of the brain; they serve both as a port of entry for calcium, which serves as a second messenger, and in part control the input-output characteristics of neurons. I have devised a preparation which allows a detailed scrutiny of the kinetics of calcium channels in mature mammalian brains. Calcium currents were measured in neurons derived from the hippocampus, neocortex, thalamus and cerebellum and could be divided into high and low threshold components. The low threshold component was prevalent in thalamus and showed conventional voltage dependent inactivation. The high threshold component was more complicated, showing both voltage and calcium dependent inactivation. Moreover I have shown that this channel responds to calcium fluxes at the mouth of the channel. Contrary to conventional thinking the high threshold component cannot be fractionated into two components; the kinetics of this channel are consistent with the existence of a single channel exhibiting complex kinetics.