[Pacemaker plasticity of the command neuron of a defensive reflex in the snail].

In an identified command neurone, a linear dependence has been found of the amplitude of the pneumostome muscles' contraction on the number of APs generated by the neurone. The adaptive nature of the motor reaction is confirmed by the existence of elementary motor acts triggered by each AP. During a series of repetitive application of intracellular rectangular electric pulses, habituation is developing in the shape of a gradual reduction of APs number and a corresponding gradual decrease of the amplitude of the pneumostome muscles' contraction. It has been shown that neuronal plasticity in response to repetitive action of the intracellular depolarizing current develops due to a change in the excitability of the pacemaker mechanism.