The effect of cholinergic, GABAergic, serotonergic, and glutamatergic receptor modulation on posttrial memory processing in the hippocampus

Though the hippocampus is widely recognized as important in learning and memory, most of the evidence for this comes from animal lesion and human pathological studies. Due to the relatively small number of drugs that have been tested in the hippocampus for their ability to alter posttrial memory processing, there is a general impression that memory processing involves only a few neurotransmitters. We have evaluated the effects of cholinergic, GABAergic, serotonergic, and glutamatergic receptor agonists and antagonists for their ability to facilitate or impair retention. CD-1 mice received acute intrahippocampal drug infusion following footshock avoidance training in a T-maze. Retention was tested 1 week after training and drug administration. The results indicate that receptor agonists of acetylcholine and glutamate improved retention, while antagonists impaired retention. However, scopolamine did not impair retention, but M1 and M2 antagonists did. Receptor agonists of serotonin and GABA impaired retention, while antagonists improved retention. Drugs acting on 5-HT-1 and 5-HT-2 as well as GABA(A) and GABA(B) receptor subtypes did not differentially effect retention.