[Changes in the sensitivity of septohippocampal responses to acetylcholine during prolonged post-tetanic potentiation].

Septo-hippocampal field evoked potentials were recorded in unanesthetized rabbits. Changes in the rapid negative component of evoked potentials (population spike) seen in acetylcholine microiontophoresis served as an index of acetylcholine sensitivity. A tendency to decreased sensitivity during long-term post-tetanic potentiation (LTPTP) and negative correlation between LTPTP and acetylcholine sensitivity were found. The evidence obtained does not support a hypothesis of changes in the mediator sensitivity as a mechanism of LTPTP. The decreased mediator sensitivity that can suppress the responses mediated through untetanized pathways is considered as an analogue of pavlovian differentiation.