Pharmacological evidence of muscarinic-cholinergic sensitization following chronic stress

Rationale: Although much evidence supports a major role of brain cholinergic transmission in memory consolidation processes, little is known about cholinergic functioning under environmental pressure. Objectives: The present experiments were aimed at investigating possible functional adaptation of muscarinic receptors promoted by a chronic stressful procedure in an inbred strain of mice highly susceptible to stress. Methods: We tested the effects of post-trial administration of a cholinergic agonist and a muscarinic antagonist on the retention of a passive avoidance task in control animals and compared these effects with those observed following food restriction. Results: Food restriction enhanced the facilitatory effects of oxotremorine and reduced the impairing effects of atropine on memory consolidation. Conclusion: Our results support the view that chronic sensitization of muscarinic receptors occurs following chronic stress.