Baum T, Becker F T
J Cardiovasc Pharmacol. 1983 Jan-Feb;5(1):121-4. doi: 10.1097/00005344-198301000-00019.
gamma-Aminobutyric acid (GABA) and GABA agonists, e.g., muscimol, reduce blood pressure and sympathetic outflow and inhibit the "carotid occlusion reflex." In contrast, muscimol exerted only marginal effects on postural reflexes in a prior study. The somatosympathetic reflex, i.e., potentials evoked in sympathetic nerves in response to sensory nerve stimulation, is a useful model for studying centrally acting drugs. Effects of muscimol on the reflex were examined in anesthetized normotensive rats. At doses which had previously been shown to reduce blood pressure but to produce only minimal attenuation of postural reflexes in conscious hypertensive rats, muscimol, administered intracerebroventricularly, reduced blood pressure and inhibited the somatosympathetic reflex in the present study. The time course of the evoked potential was not altered. Baroreceptor activation and intracerebroventricular clonidine also suppressed the reflex. The inhibitory effect of muscimol but not that of clonidine was prevented by pretreatment with the GABA antagonist bicuculline. Thus, the marked suppression of the somatosympathetic reflex by muscimol and by clonidine, in contrast to minimal effects on postural reflexes, point to the selectivity of their central inhibitory actions.
γ-氨基丁酸（GABA）及其激动剂，如蝇蕈醇，可降低血压、减少交感神经输出并抑制“颈动脉闭塞反射”。相比之下，在先前的一项研究中，蝇蕈醇对姿势反射仅产生轻微影响。躯体交感反射，即感觉神经刺激引起的交感神经电位，是研究中枢作用药物的有用模型。在麻醉的正常血压大鼠中研究了蝇蕈醇对该反射的影响。在本研究中，在先前已证明能降低血压但仅使清醒高血压大鼠的姿势反射产生最小程度减弱的剂量下，经脑室内注射蝇蕈醇可降低血压并抑制躯体交感反射。诱发电位的时间进程未改变。压力感受器激活和脑室内注射可乐定也可抑制该反射。用GABA拮抗剂荷包牡丹碱预处理可阻止蝇蕈醇的抑制作用，但不能阻止可乐定的抑制作用。因此，与对姿势反射的最小影响相反，蝇蕈醇和可乐定对躯体交感反射的显著抑制表明了它们中枢抑制作用的选择性。
