Functional characterisation of non-nitrergic non-adrenergic non-cholinergic neurotransmitter release via endocannabinoids: an in vitro study in rabbit corpus cavernosum.

Corporal smooth muscle relaxation is mediated mainly but not completely by nitric oxide. In this study possible role of endocannabinoids on non-nitrergic non-adrenergic non-cholinergic (NANC) -mediated relaxations was investigated. A total of 30 New Zealand albino male adult rabbits (4-6 months old; 3?3.5 kg body weight) were used for this study. Penises were isolated and the corpora cavernosa were then cut longitudinally into four equal strips and placed in an organ bath. The responses of tissues were recorded by isometric force displacement transducers. L-NAME abolished EFS induced relaxation responses at the lower frequencies (2-4 Hz) and inhibited the relaxation responses at higher frequencies (8-32 Hz) in the presence of atropine and guanetidine. AM251 and AM630 either together or separately inhibited whereas anandamide, ACEA and JHW015 enhanced EFS induced non-nitrergic NANC relaxation responses. Indomethacine had not any effect on AM251, AM630, anandamide, ACEA and JHW015 induced alternations. Anandamide, ACEA and JHW015 induced relaxation responses separately in pre-contracted tissues. While AM251 and AM630 inhibited anandamide-induced relaxations, capsazepine, TTX ?-conotoxin GVIA and indomethacine did not alter anandamide-induced responses. These results suggest that non-nitrergic NANC relaxations may be mediated partially by cannabinoid-like neuronal factors acting at both CB1 and CB2 receptors.