[Divergent effect of acetylcholine on processes of habituation and disinhibition].

The elaboration of habituation to repeated tactile stimuli was studied in snail (Helix pomatia) by means of intracellular recording of the neuronal activity and microionophoresis of acetylcholine (ACh). Light or a stronger tactile stimulation served as extrastimulus. The elaboration of habituation was accompanied by a rise in the threshold of action potentials (APs) generation, evoked by the habitual stimulus, and by a lowering of the threshold of APs elicited by the extrastimulus.

[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.