Inhibitory effects of the cannabinoid agonist HU 210 on rat sexual behaviour

The present study investigates the effects induced by the cannabinoid agonist HU 210 (25-100 microg/kg, administered intraperitoneally [i.p.]) on the following parameters: (a) sexual behaviour of male rats, categorised on the basis of seven consecutive mating pretests as sexually active (SA) and sexually inactive (SI) and (b) sexual receptivity of ovariectomised female rats displaying hormonally induced heat. The data obtained show that HU 210, administered in acute or subchronic mode (once daily for 7 and 14 days), impaired the copulatory pattern of SA rats in a dose- and mode-dependent manner, decreasing their sexual drive, mainly as represented by an increase in mount and intromission latencies, and affecting ejaculation mechanisms (represented as a decrease in intromission frequency and increase in ejaculation latency). After subchronic treatment with the highest dose had been suspended for 2 weeks, SA males' performance was still impaired. In SI rats, acute injections of the drug (25 and 50 microg/kg, i.p.) at the higher dose increased contact latency and decreased genital exploration time towards the female. Acute HU 210 (25-100 microg/kg, i.p.) also inhibited female sexual behaviour, potently reducing lordosis quotient and lordosis intensity.