The movement of 45Ca in brain cortex slices of guinea pigs and the influences on it of protoveratrine, ouabain, KCl and cocaine were examined. The following results were obtained.
1. Addition of azide and omission of glucose resulted in an increase in 45Ca-influx. This increase in 45Ca-influx caused by depression of the metabolism was not significantly influenced by addition of cocaine.
2. Protoveratrine, ouabain or a high concentration of KCl caused an increase in 45Ca-influx into brain slices. The increase caused by protoveratrine and ouabain was completely blocked by cocaine while that by KCl was partially blocked.
3. Efflux of 45Ca from brain slices was reduced by replacing normal Ringer by Ca-free Ringer containing EDTA.
4. There was an increase in 45Ca-efflux from brain slices on addition of protoveratrine, ouabain, KCl or azide both in normal Ringer and in Ca-free Ringer.
5. Cocaine largely prevented the increased efflux of 45Ca caused by protoveratrine and ouabain, but the increased efflux of 45Ca caused by KCl was only partially inhibited and that by azide did not seem to be affected significantly by addition of cocaine.
The role of calcium in membrane permeability and the action mechanisms of these drugs are discussed on the basis of these findings.
