地西泮对大鼠脑突触体内Ca^(2+)水平和Ca^(2+),Mg^(2+)—ATP酶活性的作用

Effects of Diazepam on Ca^(2+) Level and Ca^(2+) , Mg^(2+)-ATPase Activity in Rat Brain Synaptosomes

用Quin 2法测得大鼠脑突触体内静息游离Ca2 + 浓度 ([Ca2 + ]i)为 85± 13μmol gprotein .地西泮 0 .1,1和 10mmol L对静息突触体 [Ca2 + ]i 无明显影响 ,但能以剂量依赖方式增高 6 5mmol LKCl所致突触体 [Ca2 + ]i 升高 ,从 10 5± 2 3μmol gprotein分别达到 185± 2 8,2 6 7± 4 9和 2 91± 4 8μmol gprotein.地西泮 1和 10mmol L分别使突触体Ca2 + ,Mg2 + —ATP酶活性降低 2 8.7%和 4 2 .5 %;使Mg2 + —ATP酶活性分别降低 12 .6 %和 32 .8%,提示地西泮可能是通过抑制钙调素 ,进而抑制Ca2 + ,Mg2 + —ATP酶活性 ,使突触体 [Ca2 + ]i 升高 ,促进神经末梢释放递质 .

To elicit the correlation between facilitatory effect of diazepam on the adrenergic transmitter release and calmodulin(CaM) inhibition ,the effect of diazepam,a CaM inhibitor,on free Ca 2+ level ([Ca 2+ ] i) and Ca 2+ ,Mg 2+ -ATPase activity in rat brain synaptosomes was studied.In the Ca 2+ -free medium,resting [Ca 2+ ] i was 52±12μmol/g protein,and diazepam at 0 1,1,and 10 mmol/ L failed to elevate the [Ca 2+ ] i.In the Ca 2+ -containing medium,the resting [Ca 2+ ] i was 83+13μmol/g protein.When stimulated with KCl(65 mmol/L)+diazepam 0,0.1,1and10 mmol/L,was dose-dependently elevated to 105±23,185±28,267±49,291±48μmol/g protein respectively.It seems likely that elevation of [Ca 2+ ] i induced by diazepam is dependent on extracellular Ca 2+ concentration.Diazepam 1 and 10mmol/L inhibited activities of Ca 2+ ,Mg 2+ -ATPase and Mg 2+ -ATPase by 28.7%,42.5% and 12.6%,32.8% respectively. Ca 2+ ,Mg 2+ -ATPase is a Ca 2+ -CaM dependent ATPase.It might be that diazepam inhibits Ca 2+ ,Mg 2+ -ATPase activity by inhibiting CaM and raises the [Ca 2+ ] i,then facilitates the transmitter release.