Orer H S, Zhong S, Barman S M, Gebber G L
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
Am J Physiol. 1996 Feb;270(2 Pt 2):R333-41. doi: 10.1152/ajpregu.1996.270.2.R333.
We studied the effects of adrenoceptor agonists and antagonists on sympathetic nerve discharge (SND) of urethan-anesthetized, baroreceptor-denervated cats. In cats in which a 10-Hz rhythm coexisted with irregular 2- to 6-Hz oscillations in SND, intravenous clonidine, an alpha 2-adrenoceptor agonist, blocked the 10-Hz rhythm without affecting power at lower frequencies. In contrast, power at frequencies < or = 6 Hz was depressed by clonidine in cats in which the 10-Hz rhythm was absent. These effects were reversed by intravenous administration of alpha 2-adrenoceptor antagonists, idazoxan and rauwolscine. Rauwolscine is devoid of affinity for imidazoline receptors. Furthermore, in cats untreated with clonidine, idazoxan and rauwolscine enhanced or induced the 10-Hz rhythm without affecting power at lower frequencies. Prazosin, an alpha 1-adrenoceptor antagonist, selectively blocked the 10-Hz rhythm in SND. Finally, the 10-Hz rhythm in SND was blocked by microinjection of clonidine into the rostral or caudal ventrolateral medulla. The results support the view that central catecholaminergic neurons play a role in expression of the 10-Hz rhythm in SND.
我们研究了肾上腺素能受体激动剂和拮抗剂对氨基甲酸乙酯麻醉、压力感受器去神经支配猫的交感神经放电（SND）的影响。在SND中10赫兹节律与不规则的2至6赫兹振荡共存的猫中，静脉注射α2肾上腺素能受体激动剂可乐定可阻断10赫兹节律，而不影响较低频率的功率。相比之下，在不存在10赫兹节律的猫中，可乐定可降低频率≤6赫兹时的功率。静脉注射α2肾上腺素能受体拮抗剂咪唑克生和育亨宾可逆转这些效应。育亨宾对咪唑啉受体没有亲和力。此外，在未用可乐定处理的猫中，咪唑克生和育亨宾增强或诱导了10赫兹节律，而不影响较低频率的功率。α1肾上腺素能受体拮抗剂哌唑嗪选择性地阻断了SND中的10赫兹节律。最后，向延髓头端或尾端腹外侧微量注射可乐定可阻断SND中的10赫兹节律。这些结果支持这样一种观点，即中枢儿茶酚胺能神经元在SND中10赫兹节律的表达中起作用。
