Temperature dependence of T-type calcium channel gating

T-type calcium channel isoforms are expressed in a multitude of tissues and have a key role in a variety of physiological processes. To fully appreciate the physiological role of distinct channel isoforms it is essential to determine their kinetic properties under physiologically relevant conditions. We therefore characterized the gating behavior of expressed rat voltage-dependent calcium channels (Cav) 3.1, Cav3.2, and Cav3.3, as well as human Cav3.3 at 21 °C and 37 °C in saline that approximates physiological conditions. Exposure to 37 °C caused significant increases in the rates of activation, inactivation, and recovery from inactivation, increased the current amplitudes, and induced a hyperpolarizing shift of half-activation for Cav3.1 and Cav3.2. At 37 °C the half-inactivation showed a hyperpolarizing shift for Cav3.1 and Cav3.2 and human Cav3.3, but not rat Cav3.3. The observed changes in the kinetics were significant but not identical for the three isoforms, showing that the ability of T-type channels to conduct calcium varies with both channel isoform and temperature.