[The contrasting of synaptic signals resulting from the simultaneous modification of excitatory and inhibitory inputs].

The participation of inhibition in the long-term contrasting of neural interconnections was studied using the mathematical model of posttetanic calcium-dependent postsynaptic processes in a CA3 hippocampal pyramidal cell. It was demonstrated that if a presynaptic neuron fired during some time with a given frequency the modifiable inhibition selectively promoted the long-term potentiation of the efficacy of excitatory connection between the pre- and postsynaptic cells, while the efficacy of other inputs to the same postsynaptic cell were depressed. The long-term depression of the efficacy of disynaptic inhibitory input underlies such contrasting even in the case when the efficacy of the excitatory input is low and weakly potentiated. Concerning other inputs, we suppose that if the "common" inhibitory interneuron is simultaneously activated by different presynaptic cells, the long-term heterosynaptic potentiation of the inhibitory transmission will be induced. This effect together with the unmodifiable excitatory heterosynaptic transmission will lead to the long-term depression of the excitatory connections between various presynaptic cells and the given postsynaptic cell.