Chan J Y, Lee H C, Chan S H
Department of Medical Research, Veterans General Hospital-Taipei, Taiwan, Republic of China.
Neurosci Lett. 1991 Nov 25;133(1):81-5. doi: 10.1016/0304-3940(91)90062-x.
We investigated in adult, male Sprague-Dawley rats anesthetized with pentobarbital sodium the synaptic location of the interaction between endogenous angiotensin III (AIII) and the alpha 2-adrenoceptors in the medulla oblongata that are involved in cardiovascular regulation. The circulatory suppressant efficacy of a centrally acting alpha 2-adrenoceptor agonist, guanabenz, was used as the experimental index. Direct bilateral microinjection of AIII (40 pmol) into the nucleus reticularis gigantocellularis (NRGC), a medullary site believed to be intimately related to the cardiovascular inhibitory actions of guanabenz, attenuated, whereas the selective AIII receptor antagonist, Ile7-AIII (20 nmol), potentiated, the circulatory suppressant effects of guanabenz (100 micrograms/kg, i.v.). These two respective actions were essentially unaffected by immunocytochemically verified depletion of noradrenergic nerve terminals in the NRGC, elicited by a selective noradrenergic neurotoxin, DSP4. These data suggest that endogenous AIII may exert a tonic inhibitory action on the alpha 2-adrenoceptors located postsynaptically on neurons in the NRGC that are involved in central cardiovascular regulation.
我们在用戊巴比妥钠麻醉的成年雄性Sprague-Dawley大鼠中，研究了内源性血管紧张素III（AIII）与延髓中参与心血管调节的α2-肾上腺素能受体之间相互作用的突触位置。将一种中枢作用的α2-肾上腺素能受体激动剂胍那苄的循环抑制效能用作实验指标。将AIII（40皮摩尔）直接双侧微量注射到巨细胞网状核（NRGC）中，该髓质部位被认为与胍那苄的心血管抑制作用密切相关，这会减弱胍那苄的循环抑制作用，而选择性AIII受体拮抗剂Ile7-AIII（20纳摩尔）则会增强胍那苄（100微克/千克，静脉注射）的循环抑制作用。这两种各自的作用基本上不受选择性去甲肾上腺素能神经毒素DSP4引起的NRGC中去甲肾上腺素能神经末梢免疫细胞化学证实的耗竭的影响。这些数据表明，内源性AIII可能对NRGC中参与中枢心血管调节的神经元突触后α2-肾上腺素能受体发挥一种紧张性抑制作用。
