Melatonin attenuates Δ⁹-tetrahydrocannabinol-induced reduction in rat sperm motility and kinematics in-vitro

The use of Cannabis sativa (CS) has been widely demonstrated to have detrimental effect on male reproductive functions. Despite the well-known existence of endocannabinoid and melatonergic systems in semen, the physiological significance of their interaction is not understood. We recently showed that melatonin exacerbates the CS-induced gonadotoxicity in-vivo. To overcome the limitations associated with our in-vivo studies and further understand the role of cannabinoid-melatonin relationship in sperm functions, this study investigated the in-vitro effect of tetrahydrocannabinol (THC) and/or melatonin on motility and kinematics of capacitating rat sperms. Rat semen was randomly divided into 9 treatment groups (n = 5) as follow: Groups 1-4 were treated with placebo, SR141716 (1 mM), AM-630 (1 mM), and THC (1 mM) respectively. Groups 5-7 were pre-treated with SR141716, AM-630, and their combination respectively, followed by THC after 5 min. Group 8 was treated with melatonin (5 mM), while group 9 was treated with THC and melatonin. THC-induced reduction in sperm motility and kinematics were partly inhibited by cannabinoid receptor (CB) 1 or 2 blockade, but abolished by blockade of both CBs. Interestingly, melatonin increased the progressive motility and kinematics of rat sperms when administered alone and also attenuated THC-induced reduction in progressive motility (by 42%) and kinematics. The hyper-activated motility of capacitated sperms treated with cannabinoids and/or melatonin is determined largely by sperm velocities, amplitude of lateral head and beat/cross frequency but less by velocity ratios. Conclusively, the spermatotoxic effect of THC is mediated by CBs 1 and 2 and is ameliorated by melatonin in-vitro.