Kantor L, Hewlett G H, Gnegy M E
Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0634, USA.
J Neurosci. 1999 May 15;19(10):3801-8. doi: 10.1523/JNEUROSCI.19-10-03801.1999.
After cessation of repeated, intermittent amphetamine, we detected an emergent Ca2+-dependent component of amphetamine-induced dopamine release and an increase in calmodulin and Ca2+- and calmodulin-dependent protein kinase activity in rat striatum. This study examined the involvement of calmodulin-dependent protein kinase II (CaM kinase II) and synaptic vesicles in the enhanced Ca2+-dependent dopamine release in response to amphetamine or K+ in rat striatum. Rats were pretreated for 5 d with 2.5 mg/kg amphetamine or saline and withdrawn from drug for 10 d. The selective CaM kinase II inhibitor KN-93 (1 microM), but not the inactive analog KN-92, attenuated the Ca2+-dependent amphetamine-mediated dopamine release from amphetamine-pretreated rats but had no effect in saline-pretreated controls. [3H]Dopamine uptake was unaltered by repeated amphetamine or KN-93 and was Ca2+ independent. Striatal dopamine release stimulated by 50 mM KCl was enhanced twofold after repeated amphetamine compared with that in saline controls but was unaffected by KN-93. To examine the requirement for dopaminergic vesicles in the Ca2+-dependent dopamine release, we administered reserpine to saline- and amphetamine-pretreated rats 1 d before killing. Reserpine pretreatment did not affect amphetamine-mediated dopamine release from either pretreatment group but completely ablated K+-mediated dopamine release. Reserpine did not disrupt the ability of 1 microM KN-93 to block the Ca2+-dependent amphetamine-mediated dopamine release from amphetamine-pretreated rats. The results indicate that the enhanced dopamine release elicited by amphetamine from chronically treated rats is dependent on Ca2+- and calmodulin-dependent phosphorylation and is independent of vesicular dopamine storage. On the contrary, the enhanced depolarization-mediated vesicular dopamine release is independent of Ca2+- and calmodulin-dependent phosphorylation.
在反复间歇性给予苯丙胺后停止给药，我们检测到大鼠纹状体中出现了一种依赖Ca2+的苯丙胺诱导的多巴胺释放成分，以及钙调蛋白和Ca2+及钙调蛋白依赖性蛋白激酶活性的增加。本研究探讨了钙调蛋白依赖性蛋白激酶II（CaM激酶II）和突触小泡在大鼠纹状体中对苯丙胺或K+响应时增强的依赖Ca2+的多巴胺释放中的作用。将大鼠用2.5mg/kg苯丙胺或生理盐水预处理5天，然后停药10天。选择性CaM激酶II抑制剂KN-93（1μM），而非无活性类似物KN-92，减弱了来自苯丙胺预处理大鼠的依赖Ca2+的苯丙胺介导的多巴胺释放，但对生理盐水预处理的对照组无影响。反复给予苯丙胺或KN-93对[3H]多巴胺摄取无改变，且其摄取不依赖Ca2+。与生理盐水对照组相比，反复给予苯丙胺后，50mM KCl刺激的纹状体多巴胺释放增加了两倍，但不受KN-93影响。为了研究在依赖Ca2+的多巴胺释放中对多巴胺能小泡的需求，我们在处死前1天给生理盐水和苯丙胺预处理的大鼠注射利血平。利血平预处理对两个预处理组中苯丙胺介导的多巴胺释放均无影响，但完全消除了K+介导的多巴胺释放。利血平并未破坏1μM KN-93阻断来自苯丙胺预处理大鼠的依赖Ca2+的苯丙胺介导的多巴胺释放的能力。结果表明，长期给药的大鼠中苯丙胺引起的多巴胺释放增强依赖于Ca2+和钙调蛋白依赖性磷酸化，且与小泡多巴胺储存无关。相反，增强的去极化介导的小泡多巴胺释放与Ca2+和钙调蛋白依赖性磷酸化无关。
