Effect Of5-HT1A Receptors In The Hippocampal Dg Region On Active Avoidance Learning In Rats

Learning and memory are higher functions of the nervous system, and the relationship between these functions and neurotransmitter is a hotspot problem in research of brain functions. Serotonin (5-HT) is a classical neurotransmitter, and serotonergic pathways play an important role in the modulation of learning and memory. There are many lines of evidence showing that5-HT1A receptors play an important modulatory role in several learning and memory processes. Hippocampus is an essential structure involved in learning and memory processes, and is the main target of5-HTergic neurons from raphe nuclei. Postsynaptic5-HT1A receptors are mainly located in hippocampal DG (dentate gyrus) and CA1region. The mammalian hippocampus is cytoarchitecturally divided into the CA1, CA3, and DG, and each subregion has different function in the learning and memory. Although some studies indicate that5-HT1A receptors in the hippocampal CA1play an important roles in the hippocampus-dependent learning and memory, the roles of the5-HT and5-HT1A receptors in the DG in modulation of active avoidance learning have not been reported. Therefore, in the present study, we used an in vivo brain microdialysis technique to determine5-HT release in the DG region during active avoidance conditioned reflex, and then the antagonist or agonist of the5-HT1A receptor were microinjected into the DG region, and the active avoidance learning was measured.The results are as follows:1. In the shuttle box training, the active avoidance rate were gradually increased with the increase of the training trails, the active avoidance conditioned reflex was established on the5th training trail, and was extinct on8th training trail; the concentration of5-HT in the DG was significantly increased in6th training trail (P<0.05).2. The microinjection of WAY-100635(an antagonist of5-HT1A receptor) into the DG did not affect the numbers of training to reach the establishment-criterion and to reach the extinction-criterion in active avoidance conditioned reflex.3. Compared to the control group, the number of training to reach the establishment-criterion was significantly decreased and the number of training to reach the extinction-criterion was significantly increased in8-OH-DPAT (an agonist of5-HT1A receptor) group.Conclusion:Activation of5-HT1A receptors in DG may facilitate the active avoidance learning and memory.