Foucart S, de Champlain J, Nadeau R
Départment de physiologie, Faculté de médecine, Université de Montréal, Québec, Canada.
Can J Physiol Pharmacol. 1988 Oct;66(10):1340-3. doi: 10.1139/y88-219.
The combined effect of a beta 2-antagonist and an alpha 2-agonist on the release of adrenal catecholamines was studied in the anaesthetized and vagotomized dog. The electrical stimulation of the splanchnic nerve (5-V pulses of 2 ms duration for 3 min at a frequency of 3 Hz) produced a significant rise in adrenal catecholamine release in the adrenal vein. Intravenous injection of a beta 2-antagonist significantly reduced this response and a subsequent injection of an alpha 2-agonist further reduced the release of catecholamines. However, if the alpha 2-agonist is injected first, the release is not different compared with the control stimulation, and the subsequent injection of the beta 2-antagonist also did not modify the release in response to electrical stimulation. These results suggest that the blockade of presynaptic beta 2-receptors reduces the release of adrenal catecholamines without interfering with the activation of the alpha 2-adrenoceptors. In contrast, the pretreatment with the alpha 2-agonist, which does not modify the release of catecholamine at 3 Hz, seems to interfere with the inhibitory effect of the beta 2-antagonist.
在麻醉且切断迷走神经的犬中，研究了β2拮抗剂和α2激动剂对肾上腺儿茶酚胺释放的联合作用。刺激内脏神经（3Hz频率下，持续2ms的5V脉冲，持续3分钟）可使肾上腺静脉中肾上腺儿茶酚胺的释放显著增加。静脉注射β2拮抗剂可显著降低这一反应，随后注射α2激动剂可进一步减少儿茶酚胺的释放。然而，如果先注射α2激动剂，其释放与对照刺激相比并无差异，随后注射β2拮抗剂也不会改变电刺激引起的释放。这些结果表明，突触前β2受体的阻断可减少肾上腺儿茶酚胺的释放，而不干扰α2肾上腺素能受体的激活。相反，用α2激动剂预处理，在3Hz时并不改变儿茶酚胺的释放，似乎会干扰β2拮抗剂的抑制作用。
