STUDY OF THE LTP AND LTD OF INHIBITORY TR ANSMISSION USING MATHEMATICAL SIMULATION OF POSTSYNAPTIC PROCESSES

The mathematical model of calcium-dependent posttetanic processes in a dendritic spine of a CA(3) hippocampal pyramidal neuron which receive d excitatory and inhibitory afferents was used for studying the LTP an d LTD of inhibitory transmission. It has been demonstrated that the in hibitory synaptic efficacy is difined by GABAa and GABAb dephosphoryla tion which, in turn, is determined by the Ca2+-dependent ratio between the active protein kinases and protein phosphatases. Posttetanic decr ease/increase in intracellular Ca2+ concentration (Ca(2+)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 ra tio between the concentrations of excitatory and inhibitory transmitte rs in a synaptic cleft. The extent of inhibitory transmisson modificat ion is negligible if GABA concentration is very low or high.