Asada Y, Lee T J
Department of Pharmacology, Southern Illinois University, School of Medicine, Springfield 62794-9230.
Am J Physiol. 1992 Dec;263(6 Pt 2):H1907-10. doi: 10.1152/ajpheart.1992.263.6.H1907.
The adrenergic innervation and alpha-adrenoceptor agonist-induced constrictions in isolated medium-size pial veins (OD 734 +/- 18 microns) of the pig were investigated. Using in vitro tissue bath techniques, we noted exogenously applied norepinephrine (10(-9) to 10(-5) M) induced venoconstriction with EC50 values of 1.71 x 10(-7) M, where EC50 is the concentration that produced 50% of (non-KCl) agonist-induced maximum constriction. The constriction was mimicked by clonidine but not by phenylephrine and was more effectively blocked by yohimbine than by prazosin. Results from histochemical studies demonstrated that porcine pial veins received a denser plexus of catecholamine fluorescence fibers than do pial arteries with similar outer diameter. These results suggest that norepinephrine-induced pial venoconstriction is mediated predominantly by alpha 2-adrenoceptors and that porcine pial veins have significantly greater sensitivity to the alpha-action of norepinephrine than that reported in pial arteries. These results add further support for adrenergic innervation in pial veins being of importance in regulating cerebral blood volume and intracranial pressure.
研究了猪离体中等大小软脑膜静脉（外径734±18微米）中的肾上腺素能神经支配以及α-肾上腺素能受体激动剂诱导的收缩。使用体外组织浴技术，我们注意到外源性应用去甲肾上腺素（10^(-9)至10^(-5)M）可诱导静脉收缩，其半数有效浓度（EC50）值为1.71×10^(-7)M，其中EC50是产生（非氯化钾）激动剂诱导的最大收缩50%的浓度。可乐定可模拟这种收缩，但去氧肾上腺素不能，并且育亨宾比哌唑嗪更有效地阻断这种收缩。组织化学研究结果表明，与外径相似的软脑膜动脉相比，猪软脑膜静脉接受的儿茶酚胺荧光纤维丛更密集。这些结果表明，去甲肾上腺素诱导的软脑膜静脉收缩主要由α2-肾上腺素能受体介导，并且猪软脑膜静脉对去甲肾上腺素α作用的敏感性明显高于软脑膜动脉中的报道。这些结果进一步支持了软脑膜静脉中的肾上腺素能神经支配在调节脑血容量和颅内压方面具有重要作用。
