Moser A, Drescher S
Department of Neurology, Medical University of Lübeck, Federal Republic of Germany.
Exp Brain Res. 1990;79(2):383-7. doi: 10.1007/BF00608248.
Vasoactive intestinal polypeptide (VIP) was incubated in an adenylate cyclase assay with a particulate fraction of caudate-putamen (CP) tissue of the rat in order to examine the effect of the peptide on forskolin-activated adenylate cyclase in vitro. Forskolin induced an enhancement of cyclic AMP formation that was mediated by an effect on catalytic subunit and stimulatory guanine nucleotide regulatory protein (Ns). In our preparation, VIP did not influence basal adenylate cyclase activity or the stimulation by dopamine and sodium fluoride but, in the absence of guanylylimidodiphosphate (guanosine 5'-(beta, y-imido)-triphosphate) VIP inhibited the forskolin-stimulation of the enzyme in a noncompetitive manner. Met-encephalin, acting on a D-2 receptor-coupled putative inhibitory guanine nucleotide regulatory protein (Ni), inhibited the adenylate cyclase activity stimulated by forskolin to a slightly greater extent than VIP. When assayed together, these inhibition effects were additive, implying that the peptide receptors are not identical. The Ni-antagonist, MnCl2 completely blocked the inhibition of met-encephalin but had no significant effect on VIP-induced inhibition. In addition, pertussis toxin did not influence the effect of VIP on forskolin-stimulation in contrast to cholera toxin which did antagonize the VIP effect via the stimulatory guanine nucleotide regulatory protein (Ns). Furthermore, specific D-1 and D-2 dopaminergic receptor antagonists alpha(+)-flupentixol and spiperone had no effect on VIP-modulated forskolin-stimulated adenylate cyclase activity. These results suggest that the neuromodulatory effect of VIP is mediated by a Ns distinct from those involved in several adenylate cyclase pools sensitive to stimulation by dopamine and VIP in the rat striatum.
为了在体外研究血管活性肠肽（VIP）对福司可林激活的腺苷酸环化酶的作用，将其与大鼠尾状核 - 壳核（CP）组织的微粒体部分一起在腺苷酸环化酶测定中孵育。福司可林通过对催化亚基和刺激性鸟嘌呤核苷酸调节蛋白（Ns）的作用诱导环磷酸腺苷（cAMP）生成增强。在我们的实验准备中，VIP不影响基础腺苷酸环化酶活性或多巴胺和氟化钠的刺激作用，但在不存在鸟苷酰亚胺二磷酸（鸟苷5'-（β，γ-亚氨基）-三磷酸）的情况下，VIP以非竞争性方式抑制福司可林对该酶的刺激作用。甲硫脑啡肽作用于与D-2受体偶联的假定抑制性鸟嘌呤核苷酸调节蛋白（Ni），对福司可林刺激的腺苷酸环化酶活性的抑制程度略大于VIP。当一起测定时，这些抑制作用是相加的，这意味着肽受体并不相同。Ni拮抗剂MnCl2完全阻断了甲硫脑啡肽的抑制作用，但对VIP诱导的抑制作用没有显著影响。此外，百日咳毒素不影响VIP对福司可林刺激的作用，而霍乱毒素则通过刺激性鸟嘌呤核苷酸调节蛋白（Ns）拮抗VIP的作用。此外，特异性D-1和D-2多巴胺能受体拮抗剂α（+）-氟哌噻吨和螺哌隆对VIP调节的福司可林刺激的腺苷酸环化酶活性没有影响。这些结果表明，VIP的神经调节作用是由一种与大鼠纹状体中对多巴胺和VIP刺激敏感的几个腺苷酸环化酶池所涉及的Ns不同的Ns介导的。
