Szabo Bela, Urbanski Michal J, Bisogno Tiziana, Di Marzo Vincenzo, Mendiguren Aitziber, Baer Wolfram U, Freiman Ilka
Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität; Albertstrasse 25, D-79104 Freiburg im Breisgau, Germany.
J Physiol. 2006 Nov 15;577(Pt 1):263-80. doi: 10.1113/jphysiol.2006.119362. Epub 2006 Sep 14.
Endocannabinoids acting on CB(1) cannabinoid receptors are involved in short- and long-term depression of synaptic transmission. The aim of the present study was to determine which endocannabinoid, anandamide or 2-arachidonoylglycerol (2-AG), is involved in depolarization-induced suppression of inhibition (DSI) in the cerebellar cortex, which is the most widely studied form of short-term depression. Depolarization of Purkinje cells in the mouse cerebellum led to an increase in intracellular calcium concentration and to suppression of the inhibitory input to these neurons (i.e. DSI occurred). Orlistat and RHC80267, two blockers of sn-1-diacylglycerol lipase, the enzyme catalysing 2-AG formation, abolished DSI by acting downstream of calcium influx. In contrast, DSI occurred also in the presence of a phospholipase C inhibitor. Intact operation of the calcium-dependent messengers calmodulin and Ca(2+)-calmodulin-dependent protein kinase II were necessary for DSI. DSI was potentiated by an inhibitor of the main 2-AG-degrading enzyme, monoacylglycerol lipase. Interference with the anandamide metabolizing enzyme, fatty acid amide hydrolase, did not modify DSI. Thus, three kinds of observations identified 2-AG as the endocannabinoid involved in DSI in the mouse cerebellum: DSI was abolished by diacylglycerol lipase inhibitors; DSI was potentiated by a monoglyceride lipase inhibitor; and DSI was not changed by an inhibitor of fatty acid amide hydrolase. Further experiments indicated that 2-AG is the endocannabinoid mediating short-term retrograde signalling also at other synapses: orlistat abolished DSI in the rat cerebellum, DSI in the mouse substantia nigra pars reticulata and depolarization-induced suppression of excitation in the mouse cerebellum.
作用于CB(1)大麻素受体的内源性大麻素参与突触传递的短期和长期抑制。本研究的目的是确定哪种内源性大麻素，花生四烯乙醇胺还是2-花生四烯酸甘油酯（2-AG），参与小脑皮质中去极化诱导的抑制作用（DSI），这是研究最广泛的短期抑制形式。小鼠小脑浦肯野细胞的去极化导致细胞内钙浓度增加，并抑制对这些神经元的抑制性输入（即发生DSI）。奥利司他和RHC80267是sn-1-二酰基甘油脂肪酶的两种抑制剂，该酶催化2-AG的形成，它们通过在钙内流的下游起作用而消除了DSI。相比之下，在磷脂酶C抑制剂存在的情况下也会发生DSI。钙依赖性信使钙调蛋白和Ca(2+)-钙调蛋白依赖性蛋白激酶II的完整运作对于DSI是必需的。主要的2-AG降解酶单酰基甘油脂肪酶的抑制剂增强了DSI。干扰花生四烯乙醇胺代谢酶脂肪酸酰胺水解酶并没有改变DSI。因此，三种观察结果确定2-AG是参与小鼠小脑DSI的内源性大麻素：二酰基甘油脂肪酶抑制剂消除了DSI；单甘油酯脂肪酶抑制剂增强了DSI；脂肪酸酰胺水解酶抑制剂没有改变DSI。进一步的实验表明，2-AG也是介导其他突触短期逆行信号的内源性大麻素：奥利司他消除了大鼠小脑的DSI、小鼠黑质网状部的DSI以及小鼠小脑中去极化诱导的兴奋抑制。
