[Long-term potentiation and depression of inhibitory transmission studied by using mathematical modelling of the postsynaptic processes].

The mathematical model of calcium-dependent posttetanic processes in a dendritic spine of a CA3 hippocampal pyramidal neuron which received excitatory and inhibitory afferents was used for studying the LTP and LTD of inhibitory transmission. It has been demonstrated that the inhibitory synaptic efficacy is defined by GABAa and GABAb dephosphorylation which, in turn, is determined by the Ca(2+)-dependent ratio between the active protein kinases and protein phosphatases. Posttetanic decrease/increase in intracellular Ca2+ concentration (Ca2+p) in respect of pretetanic Ca2+ level results in an increase/decrease in number of dephosphorylated GABA receptors and in the LTP/LTD of the efficacy of inhibitory transmission. The extent of modification depends on the ratio between the concentrations of excitatory and inhibitory transmitters in a synaptic cleft. The extent of inhibitory transmission modification is negligible if GABA concentration is very low or high.