[Effects of remifentanil combined with naloxone on human sperm motility].

Objective: To observe the effects of remifentanil combined with naloxone on human sperm motility in vitro and to investigate its possible mechanism.

Methods: Twenty normal semen samples were collected, each divided into 13 aliquots, one as the control and the others treated in vitro with different concentrations of remifentanil or remifentanil + naloxone for 35 min. The percentage of progressive mobile sperm was assessed by computer-assisted sperm analysis at 5, 10, 15, 20 and 35 min.

Results: Compared with the control group, remifentanil at 0.1, 1, 10 and 100 microg/L significantly decreased sperm motility at 5 and 10 min in a dose-dependent manner, with no significant difference at 15 and 30 min; sperm motility showed no significant difference on 5 -35 min exposure to naloxone at 0.004 -0.04 mg/L, nor on 5, 10, 15 and 20 min exposure at 0.4 -4 mg/L, but was significantly increased at 35 min. Compared with the corresponding concentrations of remifentanil alone, remifentanil + naloxone remarkably increased sperm motility at 0.1 + 0.004, 1 + 0.04, 10 + 0.4, and 100 + 4 mg/L at 5 and 10 min, with no obvious difference at 15 and 30 min.

Conclusion: The onset and offset of the effect of remifentanil on sperm motility are rapid and its inhibitory effect can be antagonized by naloxone, which may be related with the micro-opioid receptor.