[Mollusk neuron habituation following extra- and intracellular administration of an ACTH fragment].

By means of intracellular recording of the mollusc neuronal activity a study was made of the influence of ACTH4-7--a fragment of the stress hormone,--on elaboration of habituation to tactile stimuli. ACTH was administered immediately after the elaboration of the series I of habituation (25 to 30 stimuli) by means of either perfusion or extra- or intracellular microionophoresis. This was followed by the II-V habituation series (with 15 min intervals between them). Perfusion and extracellular (not intracellular) ACTH4-7 administration produced an acceleration of habituation in the series II, increase of action potentials (AP) thresholds in the response to the first tactile stimulus of series II and cessation of further increase of the AP thresholds in the course of elaboration. Without ACTH, these phenomena were observed beginning with habituation series IV. The ACTH action while influencing the memory is apparently directed to the external side of the excitable neuronal membrane; ACTH seems to accelerate the consolidation process. Any of the methods of ACTH administration produced also an enhancement of EPSPs and an increase in the number of APs in the responses to stimuli, without lowering the thresholds of APs generation. This testifies toi enhanced chemosensitivity of the membrane and may underlie the influence of ACTH on the level of wakefulness.