Kuschinsky W, Wahl M
Circ Res. 1975 Aug;37(2):168-74. doi: 10.1161/01.res.37.2.168.
The question regarding the existence of an alpha-adrenergic component of pial arterial tone was investigated using a microapplication technique combined with the measurement of vascular diameter. Concentration-response curves for the alpha-receptor blocker, phentolamine, revealed no vascular reaction for a concentration range from 2.5 x 10(-11) to 2.5 x 10(-7) M. At higher concentrations (up to 1.3 x 10(-3) M) concentration-dependent dilations were observed. Constrictions of pial arteries induced by perivascular injection of 2.5 x 10(-6) M norepinephrine could be reduced by 38% and 73% when phentolamine was applied simultaneously in concentrations of 2.5 x 10(-7) and 2.5 x 10(-6) M, respectively, whereas constrictions due to 2.5 x 10(-4) M norepinephrine were not reduced by 2.5 x 10(-6) M phentolamine, indicating a competitive antagonism between norepinephrine and phentolamine for pial arteries. Stimulation of the cervical sympathetic chain (90 seconds, 10 v, 1.4 msec, 20 Hz) induced constrictions of pial arteries (mean 12%) which could be reduced by two-thirds during the simultaneous application of 2.5 x 10(-7) M phentolamine. Since the constriction induced by norepinephrine applied exogenously or released endogenously could be reduced by a concentration of phentolamine which had no vascular effect per se, we conclude that the resting tone of the pial arteries is not influenced by an alpha-adrenergic component under our experimental conditions. The dilations induced by high concentrations of phentolamine are believed to be nonspecific.
运用微量给药技术并结合血管直径测量，对软脑膜动脉张力中是否存在α-肾上腺素能成分这一问题展开了研究。α受体阻滞剂酚妥拉明的浓度-反应曲线显示，在2.5×10⁻¹¹至2.5×10⁻⁷M的浓度范围内未出现血管反应。在更高浓度（高达1.3×10⁻³M）时，观察到浓度依赖性扩张。当同时应用浓度为2.5×10⁻⁷和2.5×10⁻⁶M的酚妥拉明时，血管周围注射2.5×10⁻⁶M去甲肾上腺素所诱导的软脑膜动脉收缩可分别减少38%和73%，而2.5×10⁻⁶M酚妥拉明对2.5×10⁻⁴M去甲肾上腺素所致的收缩无减弱作用，这表明去甲肾上腺素与酚妥拉明对软脑膜动脉存在竞争性拮抗作用。刺激颈交感神经链（90秒，10伏，1.4毫秒，20赫兹）可诱导软脑膜动脉收缩（平均12%），在同时应用2.5×10⁻⁷M酚妥拉明时，收缩可减少三分之二。由于外源性应用或内源性释放的去甲肾上腺素所诱导的收缩可被本身无血管效应的酚妥拉明浓度所减弱，我们得出结论：在我们的实验条件下，软脑膜动脉的静息张力不受α-肾上腺素能成分的影响。高浓度酚妥拉明所诱导的扩张被认为是非特异性的。
