OBJECTIVETo explore the effect of morphine on male reproductive ability and its mechanisms in the rat model of morphine tolerance.

METHODSTwenty male SD rats were equally randomized to groups I (control) and II (morphine tolerance). On the 1st day, the basic paw withdrawal thermal latency (PWTL) was obtained from all the rats followed by subcutaneous injection of morphine at 10 mg/kg and then calculation of the percentage of the maximal possible effect (MPE) at 30 min after administration. On the 2nd day, the rats of group I were injected subcutaneously with saline and those of group I with morphine at 10 mg/kg bid for 7 days. Then all the rats were killed after behavioral tests and their testes and epididymides harvested for sperm counting and determina- tion of the expressions of Bax and Caspase-3 by immunohistochemistry.

RESULTSOn the 1st day, no obvious differences were ob- served between the two groups in the basic PWTL or the percentage of MPE. On the 7th day, the percentage of MPE was significantly decreased in group II as compared with group I (P < 0.05), while the basic PWTL showed no marked difference between the two groups. Group II also exhibited a significantly reduced epididymal perm count (P < 0.05) and remarkably upregulated expressions of Bax and Caspase-3 in comparison with group I.

CONCLUSIONMorphine might increase testicular cell apoptosis and reduce sperm concentration by upregulating the expressions of Bax and Caspase-3 in the rat model of morphine tolerance.