Nichols R A, Haycock J W, Wang J K, Greengard P
J Neurochem. 1987 Feb;48(2):615-21. doi: 10.1111/j.1471-4159.1987.tb04137.x.
Neurotransmitter release from rat brain synaptosomes was measured following pretreatment with various phorbol esters. Ca2+-dependent, evoked neurotransmitter release was increased by phorbol esters that were active in stimulating protein kinase C. Protein kinase C activation was demonstrated by increased incorporation of 32P into 87-kilodalton phosphoprotein, a specific substrate for that kinase. Inactive phorbol esters had no effect on neurotransmitter release or on the phosphorylation of 87-kilodalton phosphoprotein. The increased release was observed in either crude cortical synaptosomal fractions (P2) or purified cortical synaptosomal fractions. The enhancement was found for all neurotransmitters (norepinephrine, acetylcholine, gamma-aminobutyric acid, serotonin, dopamine, and aspartate), all brain regions (cerebral cortex, hippocampus, and corpus striatum), and all secretagogues (elevated extracellular K+ level, veratridine, or A23187) examined. It was also observed at all calcium concentrations present during stimulation of release. The phorbol ester enhancement of Ca2+-dependent release occurred whether or not calcium was present during pretreatment. These results indicate that stimulation of protein kinase C leads to an enhanced sensitivity of the stimulus-secretion coupling processes to calcium within the nerve terminal. The results support the possibility that presynaptic activation of protein kinase C modulates nerve terminal neurotransmitter release in the CNS.
在用各种佛波酯预处理后，测定了大鼠脑突触体中神经递质的释放。能激活蛋白激酶C的佛波酯可增加钙离子依赖的诱发性神经递质释放。通过增加32P掺入87千道尔顿磷蛋白（该激酶的一种特异性底物），证明了蛋白激酶C的激活。无活性的佛波酯对神经递质释放或87千道尔顿磷蛋白的磷酸化没有影响。在粗制皮层突触体组分（P2）或纯化的皮层突触体组分中均观察到释放增加。在所检测的所有神经递质（去甲肾上腺素、乙酰胆碱、γ-氨基丁酸、5-羟色胺、多巴胺和天冬氨酸）、所有脑区（大脑皮层、海马体和纹状体）以及所有促分泌剂（细胞外钾离子水平升高、藜芦碱或A23187）中均发现了增强作用。在刺激释放过程中存在的所有钙浓度下也观察到了这种增强作用。无论预处理期间是否存在钙，佛波酯对钙离子依赖释放的增强作用均会出现。这些结果表明，蛋白激酶C的激活导致神经末梢内刺激-分泌偶联过程对钙的敏感性增强。这些结果支持了蛋白激酶C的突触前激活调节中枢神经系统中神经末梢神经递质释放的可能性。
