Danser A H, van den Ende R, Lorenz R R, Flavahan N A, Vanhoutte P M
J Appl Physiol (1985). 1987 Feb;62(2):785-90. doi: 10.1152/jappl.1987.62.2.785.
The aim of the present study was to determine in canine bronchi the effects produced by norepinephrine (released from adrenergic nerve terminals) on cholinergic neurotransmission. Electrical stimulation of canine bronchi activates cholinergic and adrenergic nerve fibers. The adrenergic neuronal blocker, bretylium tosylate, inhibited the increase in [3H]norepinephrine overflow evoked by electrical stimulation but did not prevent that caused by the indirect sympathomimetic tyramine. During blockade of the exocytotic release of norepinephrine with bretylium, the pharmacological displacement of the sympathetic neurotransmitter by tyramine significantly decreased the contractions evoked by electrical stimulation but did not affect contractions caused by exogenous acetylcholine. Metoprolol, a beta 1-adrenergic antagonist, abolished and propranolol significantly reduced the effect of tyramine during electrical stimulation. alpha 2-Adrenergic blockade, beta 2-adrenergic blockade, or removal of the epithelium did not significantly affect the response to tyramine. These results suggest that norepinephrine when released from sympathetic nerve endings can activate prejunctional inhibitory beta 1-adrenoceptors to depress cholinergic neurotransmission in the bronchial wall.
本研究的目的是确定去甲肾上腺素（从肾上腺素能神经末梢释放）对犬支气管胆碱能神经传递产生的影响。对犬支气管进行电刺激可激活胆碱能和肾上腺素能神经纤维。肾上腺素能神经元阻滞剂溴苄铵抑制了电刺激引起的[3H]去甲肾上腺素溢出增加，但并未阻止间接拟交感神经药酪胺引起的增加。在用溴苄铵阻断去甲肾上腺素的胞吐释放过程中，酪胺对交感神经递质的药理学置换显著降低了电刺激引起的收缩，但不影响外源性乙酰胆碱引起的收缩。β1 -肾上腺素能拮抗剂美托洛尔消除了电刺激期间酪胺的作用，普萘洛尔则显著降低了该作用。α2 -肾上腺素能阻断、β2 -肾上腺素能阻断或去除上皮均未显著影响对酪胺的反应。这些结果表明，交感神经末梢释放的去甲肾上腺素可激活节前抑制性β1 -肾上腺素能受体，从而抑制支气管壁中的胆碱能神经传递。
