Involvement of Different Types of Ca2+ Currents in the Control of the Efficiency of Inhibitory Synaptic Transmission between Cultured Hippocampal Neurons

Abstract

We recorded evoked inhibitory post-synaptic currents (eIPSC) from a post-synaptic unit in a pair of synaptically connected cultured hippocampal neurons using a voltage-clamp technique in the whole-cell configuration and extracellular electrical stimulation of the pre-synaptic axon. Thirty-six neuronal pairs were examined. Dissimilar pharmacological sensitivities of eIPSC to a number of inorganic and organic blockers made it possible to estimate the involvement of different types of Ca2+ currents in Ca2+ entry into the presynaptic terminal and initiation of neurotransmitter release. Application of specific blockers of high-threshold Ca2+ channels allowed us to demonstrate that Ca2+ entry into presynaptic terminals of cultured hippocampal neurons is provided mostly by the system of high-threshold Ca2+ channels of the N- and P/Q-subtypes. The involvement of the L-subtype Ca2+ channels in the control of inhibitory transmission under study is insignificant.