THE CONTRASTING OF SYNAPTIC SIGNALS RESUL TING FROM SIMULTANEOUS MODIFICATIONS OF EXCITATORY AND INHIBITORY INPUTS

The participation of inhibition in the long-term contrasting of neural interconnections was studied using the mathematical model of postteta nic calcium-dependent postsynaptic processes in a CA3 hippocampal pyra midal cell. It was demonstrated that if a presynaptic neuron fired dur ing some time with a given frequency the modifiable inhibition selecti vely promoted the long-term potentiation of the efficacy of excitatory connection between the pre- and postsynaptic cells, while the efficac y of other inputs to the same postsynaptic cell were depressed. The lo ng-term depression of the efficacy of disynaptic inhibitory input unde rlies such contrasting even in the case when the efficacy of the excit atory input is low and weakly potentiated. Concerning other inputs, we suppose that if the <<common>> inhibitory interneuron is simultaneous ly activated by different presynaptic cells, the long-term heterosynap tic potentiation of the inhibitory transmission will be induced. This effect together with the unmodifiable excitatory heterosynaptic transm ission will lead to the long-term depression of the excitatory connect ions between various presynaptic cells and the given postsynaptic cell .