Role of Cholinergic System on the Construction of Memory and Its Interaction with Dopaminergic System

The central cholinergic system has been associated with cognitive function and memory and acetylcholine plays an important role during the early stages of memory consolidation. In this study, mice were trained with one way active avoidance procedure. Different doses of arecoline and physostigmine, with and without scopolamine, were administrated at pre-training, post-training and retrieval phases. Avoidance retention was tested at 4, 8, 12, 16 and 24 hours after training. Results showed that muscarinic agonist arecoline can potentiate memory in post training and retrieval phases and reversible cholinesterase inhibitor physostigmine potentiated memory only in retrieval phase. Scopolamine disrupted acetylcholine potentiation only in retrieval phase. In the second part of this study, the effect of dopaminergic system was investigated. Low dose of apomorphine and D2 agonist bromocriptine potentiated memory when administered in immediate post-training phase, and D2 antagonist sulpiride impaired memory. When the cholinergic system was blocked by scopolamine in immediate post-training phase, apomorphine and bromocriptine potentiated memory and sulpiride impaired it. In conclusion, these results suggest that cholinergic system plays a critical role in retrieval phase. No interaction was found between cholinergic and dopaminergic systems in the post-training phase. Acta Medica Iranica, 44(3): 172-180; 2006 © 2006 Tehran University of Medical Sciences. All rights reserved.