Low anandamide doses facilitate male rat sexual behaviour through the activation of CB1 receptors.

Rationale: Endocannabinoids (eCN) exert biphasic effects on several behaviours; however, they have only been reported to inhibit male sexual behaviour. eCN, the endogenous ligands for CB1 receptors, are released in response to neuronal stimulation and regulate the functioning of the mesocorticolimbic system (MCL), which is activated by male sexual behaviour. We hypothesised that eCN might exert biphasic effects on male rat copulatory behaviour and be released during copulation to satiation as a result of the repeated activation of the MCL system.

Objectives: The study was conducted to determine if the eCN anandamide exerts biphasic effects on sexual behaviour expression of sexually experienced and sexually satiated male rats and to establish the possible participation of eCN in the sexual satiation phenomenon.

Methods: The eCN anandamide and the CB1 receptor antagonist AM251 were systemically administered to sexually experienced or sexually satiated rats and their effects on copulatory behaviour analysed.

Results: Low anandamide doses facilitated sexual behaviour expression in sexually experienced and in sexually satiated rats by acting at CB1 receptors. AM251 blocked the establishment of the sexual inhibition that characterises sexual satiation, but did not reverse it once established.

Conclusions: Anandamide exerts dose-based biphasic effects on copulatory behaviour of sexually experienced male rats and facilitates sexual behaviour expression of sexually satiated animals at low doses. eCN participate in the establishment, but not in the maintenance of the sexual inhibitory state that characterises the sexual satiation phenomenon.