Lorenz R R, Vanhoutte P M, Shepherd J T
Blood Vessels. 1979;16(3):113-25. doi: 10.1159/000158198.
Experiments were performed to determine the conditions in which norepinephrine release from adrenergic nerve terminals in smooth muscle from canine blood vessels and spleen might be inhibited by prejunctional alpha-adrenergic receptor activation. Strips of aorta, mesenteric and splenic arteries, splenic capsule and portal and saphenous veins were labeled with 7-3H-norepinephrine and mounted for superfusion. In the portal vein, an inhibitory effect of prejunctional receptor activation with exogenous norepinephrine (1.2 X 10(-6) M) on transmitter efflux could be demonstrated during electrical stimulation (9 V, 2 Hz) of the nerve terminals. By contrast, in the other tissues, inhibition of transmitter release during electrical stimulation or depolarization of the nerve terminals with K+ (40 mEq/l) could only be demonstrated aftet blockade of the neuronal uptake mechanism. That activation of prejunctional alpha-adrenergic receptors in blood vessels inhibits the exocytotic process is suggested by the failure of exogenous norepinephrine to affect either the basal efflux of 3-H-norepinephrine or the displacement of 3H-norepinephrine by tyramine.
进行了一些实验，以确定犬类血管和平滑肌中去甲肾上腺素能神经末梢释放去甲肾上腺素的过程在何种条件下可能会被节前α-肾上腺素能受体激活所抑制。用7-³H-去甲肾上腺素标记主动脉、肠系膜动脉和脾动脉、脾包膜以及门静脉和大隐静脉的条带，并安装用于灌注。在门静脉中，在对神经末梢进行电刺激（9伏，2赫兹）期间，可证明外源性去甲肾上腺素（1.2×10⁻⁶摩尔/升）激活节前受体对递质外流有抑制作用。相比之下，在其他组织中，只有在阻断神经元摄取机制后，才能证明在对神经末梢进行电刺激或用钾离子（40毫当量/升）使其去极化期间递质释放受到抑制。外源性去甲肾上腺素未能影响³H-去甲肾上腺素的基础外流或酪胺对³H-去甲肾上腺素的置换，这表明血管中节前α-肾上腺素能受体的激活抑制了胞吐过程。
