The neurosteroids pregnenolone and pregnenolone-sulfate but not progesterone, block Ca 2+ currents in acutely isolated hippocampal CA1 neurons

Abstract

The neurosteroids pregnenolone (PE) and pregnenolone-sulfate (PS) have been shown to interact with the GABA A receptor in the central nervous system. In contrast, nothing is known of any possible modulation of voltage-gated calcium channels (VGCC). We have examined the interaction of PE, PS and progesterone on VGCC in acutely isolated adult guinea-pig hippocampal CA1 neurons using the whole-cell patch clamp technique. PE and PS depressed the calcium current at low micromolar concentrations (0.001 – 100 μM). The time to peak of the calcium current was slowed by PE and PS. The blocking action of PE and PS occurs in the presence of 10 μM picrotoxin. In contrast, progesterone had no effect on the Ca 2+ current, indicating specificity for PE and PS. These results demonstrate a direct and novel membrane site of action for PE and PS, suggesting a possible role influencing brain excitability.