1. Possible inhibitory roles of endogenous 2-arachidonoylglycerol during corticotropin-releasing factor-induced activation of central sympatho-adrenomedullary outflow in anesthetized rats
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Shimizu, Takahiro, Lu, Lianyi, and Yokotani, Kunihiko
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CORTICOTROPIN releasing hormone , *ENZYME activation , *ADRENOMEDULLIN , *ANESTHESIA , *LABORATORY rats , *ENZYME inhibitors , *BRAIN physiology , *CANNABINOIDS - Abstract
Abstract: We previously reported that intracerebroventricularly (i.c.v.) administered corticotropin-releasing factor (CRF) (0.5–3.0nmol/animal) dose-dependently elevates plasma noradrenaline and adrenaline through brain phospholipase C-, diacylglycerol lipase- and prostanoids-mediated mechanisms in rats. Diacylglycerol produced by phospholipase C from phospholipids can be hydrolyzed by diacylglycerol lipase into 2-arachidonoylglycerol, which may be further hydrolyzed by monoacylglycerol lipase into arachidonic acid, a precursor of prostanoids. Recently, 2-arachidonoylglycerol has been recognized as a major brain endocannabinoid, which can modulate synaptic transmission through presynaptic cannabinoid CB1 receptors. Released 2-arachidonoylglycerol is rapidly deactivated by uptake into cells and enzymatic hydrolysis. In the present study, therefore, we examined (1) the involvement of brain 2-arachidonoylglycerol, (2) the regulatory role of 2-arachidonoylglycerol as a brain endocannabinoid, and (3) the effect of exogenous cannabinoid receptor agonist, on the CRF-induced elevation of plasma noradrenaline and adrenaline using anesthetized rats. The elevation of both catecholamines induced by a submaximal dose of CRF (1.5nmol/animal, i.c.v.) was reduced by i.c.v. administered MAFP (monoacylglycerol lipase inhibitor) (0.7 and 1.4µmol/animal), AM 404 (endocannabinoid uptake-inhibitor) (80 and 250nmol/animal) and ACEA (cannabinoid CB1 receptor agonist) (0.7 and 1.4µmol/animal), while AM 251 (cannabinoid CB1 receptor antagonist) (90 and 180nmol/animal, i.c.v.) potentiated the response induced by a small dose of CRF (0.5nmol/animal, i.c.v.). These results suggest a possibility that 2-arachidonoylglycerol is endogenously generated in the brain during CRF-induced activation of central sympatho-adrenomedullary outflow, thereby inhibiting the peptide-induced response by activation of brain cannabinoid CB1 receptors in anesthetized rats. [Copyright &y& Elsevier]
- Published
- 2010
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