THE POST-TRAINING MEMORY ENHANCEMENT INDUCED BY PHYSOSTIGMINE AND OXOTREMORINE IN MICE IS NOT STATE-DEPENDENT

Immediate post-training subcutaneous administration of either the cent rally acting anticholinesterase physostigmine (35, 70, or 150 mu g/kg) or the centrally acting muscarinic cholinergic agonist oxotremorine ( OTM; 25, 50, or 100 mu g/kg) significantly enhanced retention of male Swiss mice tested 48 h after training in a one-trial step-through inhi bitory avoidance task (0.8 mA, 50 Hz, Is footshock). Neither physostig mine nor OTM affected latencies to step through in mice not given the footshock on the training trial, suggesting that the effects of both c holinomimetics on retention performance were not due to nonspecific ac tions on response test latencies. The peripherally acting anticholines terase neostigmine (35, 70, or 150 mu g/kg) did not significantly infl uence retention latencies of either shocked or unshocked mice. The inf luences of physostigmine (150 mu g/kg) and OTM (100 mu g/kg) on retent ion were time-dependent, which suggests that the drugs facilitated mem ory storage. Administration of physostigmine (150 mu g/kg) or OTM (100 mu g/kg) 30 min prior to the retention test did not affect the retent ion performance of mice given post-training injections of either salin e, physostigmine (150 mu g/kg), or OTM (100 mu g/kg). Considered toget her, these findings indicate that the memory-enhancing effects of post -training administration of physostigmine or OTM are not state-depende nt and are consistent with the view that the behavioral effects of the cholinomimetics drugs are mediated through an interaction with the ne ural processes underlying the storage of acquired information. (C) 199 6 Academic Press, Inc.