The different susceptibility of the changes in synaptic interface structural in hippocampal CA1 area of morphine dependent rats

Abstract

Objective To investigate changes of synaptic interface structural in the hippocampus Cal in high and low conditioned place preference(CPP) rats after chronic morphine treatment.Methods The male SD rats were randomly distributed to experiment group 130 cases(intraperitoneal injected morphine twice a day for ten days in an ascending dosage schedule) and control group 30 cases(injected saline of the same volume at same time).The rats in experiment group were re-classified into high preference group(HP),middle group and low preference group(LP) according to the numerical value of the CPP.The middle group was rejected.The rats in HP and LP were scarified at the time of 3h,3d and 14d after the last injection.The hippocampus Cal were removed and prepared for electron microscope specimen.The synaptie interface structure parameter were analyzed by image processing technique.Results ①No significant difference of pretest scores staying at the non-preference chambet existed among the three groups(F=0.78,P=0.47).However,the test scores of the CPP minus the time stayed at pretest natural preference in the high group was significantly higher than that of the low group(P=0.00).②At the 3h and 3d,the PSD of the high group((15.20±-3.65)nm) was significantly lower than low group((17.63±6.61)nm,P<0.01);the synaptic cleft of high group((5.77±2.08)nm) was significantly higher than low group ((4.92±1.65)nm,P<0.05).At the 14d,the PSD of the high group((16.22±4.93)nm) was significantly lower than low group((18.42±3.78)nm,P<0.01).Conclusion In hippocampal Cal area the synaptic cleft in the HP group was higher than that of LP group,the post-synaptic density in the HP group was lower than that of LP group.These changes may be the synaptic basic of the different susceptibility. Key words: Morphine dependence; Conditioned place preference; Synaptic interface structure; Susceptibility