O'Halloran K D, Herman J K, Bisgard G E
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, 53706, USA.
Respir Physiol. 1999 Oct 15;118(1):15-24. doi: 10.1016/s0034-5687(99)00069-9.
To assess the influence of vagal afferent feedback in the development of respiratory instabilities induced by alpha2-adrenoceptor (alpha2-AR) stimulation in the goat, we examined the ventilatory effects of clonidine, an alpha2-AR agonist, in awake tracheostomized goats before and after bilateral mid-cervical vagotomy. Prior to vagal section, systemic administration of clonidine (0.5-3.0 microg kg(-1)) induced a highly dysrhythmic pattern of breathing in all animals that was characterized by alternating episodes of tachypnea and slow irregular breathing patterns including prolonged and variable expiratory time (TE) intervals. Periods of apnea were commonly observed. Bilateral vagotomy resulted in a slower deeper breathing pattern and abolished the tachypnea evoked by intravenous administration of phenylbiguanide (PBG; 20-50 microg kg(-1)), a selective serotonin type 3 (5-HT3) receptor agonist. However, respiratory disturbances associated with alpha2-AR stimulation (including tachypnea) persisted after vagal section and were qualitatively and quantitatively similar to pre-vagotomy data demonstrating that vagal afferent feedback is not necessary for the development of respiratory disturbances induced by clonidine. The results suggest that respiratory dysrhythmias caused by alpha2-AR agonists in the goat are mediated by alpha2-ARs in the CNS.
为了评估迷走神经传入反馈在山羊中由α2-肾上腺素能受体（α2-AR）刺激诱发的呼吸不稳定发展过程中的影响，我们在双侧颈中段迷走神经切断术前和术后，检查了α2-AR激动剂可乐定对清醒气管切开山羊的通气效应。在迷走神经切断术前，对所有动物全身给予可乐定（0.5 - 3.0微克/千克）均诱发了高度心律失常的呼吸模式，其特征为呼吸急促和缓慢不规则呼吸模式交替出现，包括延长且可变的呼气时间（TE）间隔。常观察到呼吸暂停期。双侧迷走神经切断导致呼吸模式变慢变深，并消除了静脉注射苯乙双胍（PBG；20 - 50微克/千克）（一种选择性5-羟色胺3型（5-HT3）受体激动剂）所诱发的呼吸急促。然而，与α2-AR刺激相关的呼吸紊乱（包括呼吸急促）在迷走神经切断术后仍然存在，并且在质量和数量上与迷走神经切断术前的数据相似，这表明迷走神经传入反馈对于可乐定诱发的呼吸紊乱的发展并非必需。结果表明，山羊中由α2-AR激动剂引起的呼吸心律失常是由中枢神经系统中的α2-AR介导的。
