Effect of nifedipine in high concentrations on inhibitory synaptic transmission

Effect of nifedipine on inhibitory postsynaptic currents (IPSC) was studied in cultured hippocampal neurons. Nifedipine, if used in low concentrations, caused no essential changes in the IPSC amplitude. If used in high concentrations (50 or 100 μM), this calcium channel blocker reduced the IPSC amplitude, on the average, by 35 and 42%, respectively. The calcium current component sensitive to nifedipine at high concentrations was found to be insensitive to the agents, which block calcium channels of N- and P/Q types. It is concluded that the L-type calcium channels sensitive to nifedipine in low concentrations are absent in the presynaptic membrane of inhibitory synapses, whereas the only component of calcium current sensitive to this blocking agent in a high concentration, as well as the ω-CTx-GVIA- and ω-Aga-IVA-sensitive components of this current, participate in the transmission of inhibitory synaptic influences on the neurons studied.