[Selective decrease in neuron excitability during habituation].

By means of the intracellular recording a study was made of the habituation to tactile stimuli in Helex pomatia neurones and of the influence of acetylcholine (ACh) microionphoresis on the response to a habituating stimulus in those units which before habituation reduced the reaction to a tactile stimulus under the action of ACh. Habituation was attended with a diminution of EPSP and of the action potential (AP) elicited by the habituating stimulus. The AP generation threshold and the probability of AP blockade increased with stimuli repetition. An extra stimulus produced in the neurones a greater AP at a lower threshold. After habituation elaboration, Ach increased the neurone response to the habituating stimulus: EPSP and the probability of AP generation increased, while the AP threshold was lowered. At the interaction of the activated synapses with the neurone, the electrogenic and chemical properties of its membrane may probably change for a short time so that the threshold and the AP and EPSP amplitude may differ for the stimuli with different biological significance.