Effect of dopamine D1 receptor in hippocampal DG region in active avoidance learning in rats and its mechanism / 吉林大学学报(医学版)

ABSTRACT

Objective: To observe the changes of dopamine (DA) levels in the hippocampal dentate gyrus (DG) region of the rats during the establishment and extinction process of active avoidance conditioned reflex, and to investigate the effect of D1 receptor in the active avoidance learning of the rats and its mechanism. Methods: A total of 24 male SD rats were randomly divided into non-training group, training group, control group and SCH group (n= 6). The rats in training group were trained for active avoidance whereas the rats in non-training group were only put into the shuttle box without training, and then the DA levels in extracellular fluid in DG region of the rats in two groups were measured. In control and SCH groups, the saline or SCH-23390 was injected into the DG region of the rats before the active avoidance training, and then the glutamate (Glu) levels and the field excitatory postsynaptic potential (fEPSP) amplitudes in extracellular fluid in DG region of the rats in two groups were examined. The rates of active avoidance of the rats were recorded by behavioral analysis system of the shuttle box. The levels of DA and Glu in DG region of the rats were measured by microdialysis and HPLC techniques, and the amplitude of fEPSP in DG region of the rats was examined by electrophysiological recording. Results: The DA level in DG region of the rats in training group was gradually increased during the establishment process and was gradually decreased during the extinction process of conditioned reflex; compared with the 1st day, the DA level in DG region of the rats on the 5th day was markedly increased (P0. 05). In control group, the rats reached the establishment criterion on the 5th day (active avoidance rate > 65%) and reached the criterion of extinction on the 7th day (active avoidance rate 0. 05). Compared with control group, the Glu level and fEPSP amplitude of the rats in SCH group on the 5th day were markedly decreased (P<0. 05). Conclusion: DA in hippocampal DG region of the rats can facilitate the active avoidance learning via activation of D1 receptors, and its mechanism is associated with the enhancement of Glu level and synaptic transmission efficiency.