Investigation of cannabinoids effects on the cholinergic neurotransmission in isolated rabbit gastric fundus

It is known that cannabinoid agonists act on cholinergic transmission to reduce smooth muscle contractility in different regions of gastrointestinal tract. This study?s aim is to investigate cannabinoids effects on cholinergic transmission responses which are mediated electrical field stimulation in isolated rabbit gastric fundus smooth muscle and also these likely effects can be on which cannabinoid receptors. In the experiments 2,5-3 kg of 30 albino rabbits gastric smooth muscle strips obtained from the organ bath containing Krebs solution isometric force transducer for recording of isometric contractions of the way that they are connected. Guanetidine and indomethacin had any effect on the contractile responses mediated electrical field stimulation (EFS).While atropine was abolished contractile responses, neostigmine was enhanced contractile responses via EFS. Although ?-conotoxin GVIA was decreased the contractions significantly. These results show that contractile responses, which was obtained from gastric fundus caused by EFS, depend on neurally stimulation and take it?s source from cholinergic neurons. In the presence of guanetidine and indomethacin anandamide, WIN 55,212-2, ACEA and JWH015 produced a concentration-dependent reduction of EFS-evoked cholinergic contractions. CB1 receptor antagonist AM 251, CB2 receptor antagonist AM 630 and together with two antagonists are existed reduced inhibitory effects induced by anandamide. Although while inhibitory effects of WIN 55,212-2 was reduced more in low concentrations in the existence of AM 630, AM 251 and together with two antagonists had any effects on inhibitory effects of WIN 55,212-2. While AM 251 reduced the effects of ACEA, AM 630 attenuated the effects of JWHO15. AM 251 was enhanced cholinergic contractions induced by EFS, but AM 630 had any effect on the contractions. While anandamide, WIN 55,212-2 and ACEA didn?t cause relaxation in tissues precontracted with noradrenaline, JWH015 caused relaxation in these tissues. These findings indicate that endocannabinoids have presynaptic effects on cholinergic contractions via CB1 and CB2 receptors in isolated rabbit gastric fundus.Key Words:Endocannabinoids, rabbit gastric fundus, electrical field stimulation