Action of hypoxia on different types of calcium channels in hippocampal neurons

Whole-cell patch clamp and polarographic oxygen partial pressure (pO(2)) measurements were used to establish the sensitivity of high-voltage-activated (HVA) Ca2+ channel subtypes of CA1 hippocampal neurons of rats to hypoxic conditions. Decrease of pO(2) to 15-30 mm Hg induced a potentiation of HVA Ca2+ currents by 94%. Using selective blockers of N- and L-types of calcium channels, we found that inhibition of L-type channels decreased the effect by 54%, whereas N-type blocker attenuated the effect by 30%. Taking into account the ratio of currents mediated by these channel subtypes in CA1 hippocampal neurons, we concluded that both types of HVA Ca2+ channels are sensitive to hypoxia, however, L-type was about 3.5 times more sensitive to oxygen reduction. (C) 2003 Elsevier B.V All rights reserved.