calcimycin and glyceryl-2-arachidonate

2-arachidonoylglycerol (2-AG) is an endogenous ligand for the cannabinoid receptors with a variety of potent biological activities. In this study, we first examined the effects of potassium-induced depolarization on the level of 2-AG in rat brain synaptosomes. We found that a significant amount of 2-AG was generated in the synaptosomes following depolarization. Notably, depolarization did not affect the levels of other molecular species of monoacylglycerols. Furthermore, the level of anandamide was very low and did not change markedly following depolarization. It thus appeared that the depolarization-induced accelerated generation is a unique feature of 2-AG. We obtained evidence that phospholipase C is involved in the generation of 2-AG in depolarized synaptosomes: U73122, a phospholipase C inhibitor, markedly reduced the depolarization-induced generation of 2-AG, and the level of diacylglycerol was rapidly elevated following depolarization. A significant amount of 2-AG was released from synaptosomes upon depolarization. Interestingly, treatment of the synaptosomes with SR141716A, a CB1 receptor antagonist, augmented the release of glutamate from depolarized synaptosomes. These results strongly suggest that the endogenous ligand for the cannabinoid receptors, i.e. 2-AG, generated through increased phospholipid metabolism upon depolarization, plays an important role in attenuating glutamate release from the synaptic terminals by acting on the CB1 receptor.

Topics: Animals; Arachidonic Acids; Brain; Calcimycin; Calcium Channel Blockers; Camphanes; Diglycerides; Endocannabinoids; Estrenes; Fatty Acids; Glycerides; Male; Membrane Potentials; Neuromuscular Depolarizing Agents; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Pyrrolidinones; Rats; Rats, Wistar; Receptors, Cannabinoid; Rimonabant; Synaptosomes

We investigated whether 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand, is involved in acetylcholine- and calcium ionophore A23187-induced relaxations in the presence of N(G)-nitro-L-arginine methyl ester (L-NAME) and indomethacin, which is considered to be mediated by endothelium-derived hyperpolarizing factor (EDHF). In rabbit mesenteric arterial rings pre-constricted with noradrenaline, 2-arachidonoylglycerol caused concentration-dependent relaxation. The 2-arachidonoylglycerol-induced relaxations were not affected by endothelium removal. N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-caroxamide (SR141716A) and 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morholinyl-1H-pyrazole-3-carboxamide (AM281), cannabinoid CB(1) receptor antagonists, significantly attenuated 2-arachidonoylglycerol-induced relaxation and the acetylcholine-induced relaxation only slightly, but not the calcium ionophore A23187-induced relaxation. On the other hand, charybdotoxin plus apamin, K(+) channel blockers, significantly attenuated acetylcholine and calcium ionohore A23187-induced relaxations but not 2-arachidonoylglycerol-induced relaxations. These results suggest that 2-arachidonoylglycerol can cause relaxations via cannabinoid CB(1) receptors, but is not involved in EDHF-mediated relaxations.

Topics: Animals; Arachidonic Acids; Biological Factors; Calcimycin; Calcium Channel Blockers; Endocannabinoids; Glycerides; Ionophores; Male; Neurotransmitter Agents; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Rabbits; Receptors, Cannabinoid; Receptors, Drug; Rimonabant; Vasodilation

Human vascular endothelial cells were found to generate and release 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand, upon stimulation with thrombin or A23187. We confirmed that vascular smooth muscle cells as well as endothelial cells possess cannabinoid CB1 receptor mRNA. 2-Arachidonoylglycerol, generated in vascular tissues, may play an important role in modulating vascular tone through acting on the cannabinoid CB1 receptor expressed on vascular smooth muscle cells, endothelial cells as well as peripheral nerve terminals.

Topics: Aorta; Arachidonic Acid; Arachidonic Acids; Calcimycin; Cells, Cultured; Diglycerides; Endocannabinoids; Endothelium, Vascular; Glycerides; Humans; Kinetics; Muscle, Smooth, Vascular; Receptors, Cannabinoid; Receptors, Drug; RNA, Messenger; Thrombin; Tritium; Umbilical Veins