摘要：To clarify the physiological roles of muscarinic acetylcholine (mACh) receptor subtypes, M1 and M2, on learning and memory, we examined the effects of three antagonists, atropine (non-selective), pirenzepine (M1 selective) and 11-[[2-[(diethylamino)methyl]-1-piperidinyl]acetyl]-5, 11-dihydro-6H-pyrido[2, 3-b][1, 4]benzodiazepine-6-one, AF-DX 116 (M2 selective), on step-through passive avoidance tasks in mice. During acquisition tests, mice were trained repeatedly until they achieved criterion latency (300 s). In all experiments, drugs or vehicles were intracerebroventricularly administered. Pre-training (5 min before) administration of atropine (1-40 nmol) and pirenzepine(10 and 40 nmol) shortened the response latency in retention tests at 14 d after acquisition training. Pre-test (5 min before) and post-training (immediately after the acquisition training) administration of atropine slightly but not significantly impaired retention scores. The administration of AF-DX 116 did not apparently affect the scores in any of tests. Thus, the M1 receptor subtype coupling systems seem to be more important in the acquisition-consolidation process rather than in the retrieval process.
