Hedrick M S, Ryan M L, Bisgard G E
Dept. of Biological Sciences, California State University, Hayward 94542, USA.
Respir Physiol. 1995 Aug;101(2):129-37. doi: 10.1016/0034-5687(95)00030-h.
The purpose of this study was to test the hypothesis that respiratory and apneas induced by alpha 2 agonists in anesthetized goats are associated with an increase of upper airway expiratory-related activity, rather than a general depression of breathing. Activities of phrenic (Phr) and recurrent laryngeal nerves (RLN) were recorded in response to the alpha 2 agonists clonidine (0.5-3.0 microgram.kg-1 i.v.) or guanabenz (7.0-20.0 micrograms.kg-1 i.v.) in ten chloralose-anesthetized goats. Injection of either alpha 2 agonist resulted in respiratory arrhythmias with a greater than seven-fold increase in TE and a 30% reduction in TI. During apneas RLN expiratory-related activity remained tonic until the next Phr burst, consistent with our hypothesis. Cessation of Phr activity during hypocapnia also resulted in a tonic increase of RLN expiratory activity; and injection of NaCN (50 micrograms.kg-1 i.v.) increased Phr and RLN inspiratory activities, while attenuating RLN expiratory-related activity. Inspiratory and expiratory-related activity of RLN motoneurons appear to be reciprocally modulated by alpha 2 agonists or changes in central or peripheral chemoreceptor drive. The results indicate that central apneas and respiratory arrhythmias may be associated with alpha 2-adrenoceptor modulation of laryngeal expiratory-related activity.
在麻醉山羊中，α2激动剂诱发的呼吸和呼吸暂停与上呼吸道呼气相关活动增加有关，而非与呼吸的普遍抑制有关。在十只氯醛糖麻醉的山羊中，记录了膈神经（Phr）和喉返神经（RLN）对α2激动剂可乐定（0.5 - 3.0微克·千克-1静脉注射）或胍那苄（7.0 - 20.0微克·千克-1静脉注射）的反应。注射任何一种α2激动剂均导致呼吸心律失常，呼气时间（TE）增加超过七倍，吸气时间（TI）减少30%。在呼吸暂停期间，RLN呼气相关活动保持紧张性直至下一次膈神经爆发，这与我们的假设一致。低碳酸血症期间膈神经活动停止也导致RLN呼气活动紧张性增加；静脉注射NaCN（50微克·千克-1）增加了膈神经和RLN吸气活动，同时减弱了RLN呼气相关活动。RLN运动神经元的吸气和呼气相关活动似乎受到α2激动剂或中枢或外周化学感受器驱动变化的相互调节。结果表明，中枢性呼吸暂停和呼吸心律失常可能与α2肾上腺素能受体对喉部呼气相关活动的调节有关。
