大鼠纹状体突触体酪氨酸羟化酶自身调节的研究

STUDIES ON AUTOREGULATION OF TYROSINE HYDROXYLASE IN RAT CORPUS STRIATUM

依赖Ｃａ２＋／ＣａＭ的ＰＫⅡ和依赖Ｃａ２＋／ＰＩ的ＰＫＣ对大鼠纹状体突触体的磷酸化均显著激活酪氨酸羟化酶（ＴＨ）的活性，增加Ｌｄｏｐａ的生成。选择性Ｄ２受体激动剂ＬＹ１７１５５５不影响ＰＫⅡ和ＰＫＣ对ＴＨ的磷酸化激活。ＣａＭ拮抗剂Ｗ７和去除反应液中的Ｃａ２＋均不影响Ｋ＋６０ｍｍｏｌ／Ｌ去极化对纹状体ＴＨ的激活，而ＰＫＣ抑制剂多粘菌素Ｂ却能完全阻滞Ｋ＋去极化对ＴＨ的激活效应。研究结果表明：（１）多巴胺（ＤＡ）自身受体介导的自身递质生物合成的负反馈调控与ＰＫⅡ和ＰＫＣ对ＴＨ的磷酸化激活不偶联；（２）Ｋ＋去极化对ＴＨ的激活是由ＰＫＣ介导的，不受ＤＡ自身受体的调控。

ynaptosomes isolated from rat striatum were used as a studying model so as to search into the correlation between Ca 2+ dependent protein kinases and autoregulation of tyrosine hydroxylase(TH). In the presence of Ca 2+ calmodulin (CaM)/protein kinae Ⅱ(PKⅡ)and protein kinase C activator phorbol 12, 13 dibutyrate (PRB), striatal TH was stimulated and therefore the biosynthesis of L dopa was increased significantly. Moreover, selective D 2 dopamine (DA) receptor agonist LY171555 failed to affect the actvations of Ca 2+ CaM/PKⅡ and PRB on synaptosomal TH. In addition, neither CaM antagonist W7 nor Ca 2+ removal from reaction medium was able to affect K + depolarization induced activation of striatal synaptosomal TH. However,polymyxin B(PMB), an inhibitor of PKC, could completely block this activation. These results indicate 1) the negative feedback regulation of DA biosynthesis mediated by DA autoreceptors is not coupled with the phosphorylation and activation of PKⅡ and PKC on TH, and 2) the activation of K + depolarization on TH is mediated by PKC rather by PKⅡ and is not regulated by DA autoeceptors.