Horner R L, Kubin L
Center for Sleep and Respiratory Neurobiology, University of Pennsylvania, Philadelphia 19104-4283, USA.
Neuroscience. 1999;93(1):215-26. doi: 10.1016/s0306-4522(99)00126-8.
Microinjection of a cholinergic agonist, carbachol, into the pontine reticular formation of chronically instrumented intact or acutely decerebrate rats and cats has been used extensively to study rapid eye movement sleep mechanisms. In this study, we sought to develop a reduced carbachol model of rapid eye movement sleep-like neural events exhibiting multiple physiological markers of this state, and allowing for the use of invasive electrophysiological techniques. Accordingly, we investigated whether pontine carbachol could produce rapid eye movement sleep-like motor atonia and electrocortical changes in urethane-anaesthetized rats. We recorded cortical and hippocampal electroencephalograms and genioglossus and inspiratory intercostal muscle activities in 13 urethane-anaesthetized, spontaneously breathing, tracheotomized and vagotomized rats. In steady-state periods with high-voltage/low-frequency electroencephalogram activity, carbachol microinjections (15-40 nl, 10 mM) were placed in the medial pontine reticular formation. In 12 rats, carbachol elicited episodes of stereotyped hypotonia of genioglossus but not intercostal muscle activity, typical of rapid eye movement sleep, with a latency and duration of 2.2+/-0.3min (mean+/-S.E.M.) and 11.0+/-2.9 min, respectively. In four of these rats, also similar to rapid eye movement sleep, the major suppression of genioglossus activity (-74+/-9%) was accompanied by electroencephalogram desynchronization, appearance of hippocampal theta rhythm, and a respiratory rate increase (+ 14+/-3%). In the remaining eight rats, the stereotyped suppression of genioglossus activity (-48+/-3%) occurred without electroencephalogram desynchronization and hippocampal theta, and was accompanied by a respiratory rate decrease (-6+/-2%); a pattern of response typical of decerebrate animals. Within a rat, similar patterns of response to repeated carbachol injections at the same anatomical site were obtained. Pontine atropine prevented responses to subsequent carbachol injections. Thus, in urethane-anaesthetized rats, pontine carbachol consistently produced a differential suppression of pharyngeal versus respiratory pump muscle activity, and in a subset of animals, this was also accompanied by cortical and hippocampal electrographic changes typical of rapid eye movement sleep. This shows that complex and stereotyped neuronal events underlying both ascending and descending signs of rapid eye movement sleep can be pharmacologically activated under general anaesthesia. Such a reduced preparation may be useful for studies into the central neuronal mechanisms underlying generation of rapid eye movement sleep; particularly for studies requiring techniques that are difficult to implement in intact, naturally sleeping animals. The acceleration of the respiratory rate observed only when carbachol induced electroencephalogram desynchronization suggests that neural events associated with electrocortical changes contribute to the respiratory rate increases observed in natural rapid eye movement sleep.
向长期植入仪器的完整或急性去大脑的大鼠和猫的脑桥网状结构微量注射胆碱能激动剂卡巴胆碱，已被广泛用于研究快速眼动睡眠机制。在本研究中，我们试图建立一种简化的卡巴胆碱模型，该模型能产生类似快速眼动睡眠的神经事件，并表现出该状态的多种生理标志物，同时允许使用侵入性电生理技术。因此，我们研究了脑桥注射卡巴胆碱是否能在乌拉坦麻醉的大鼠中产生类似快速眼动睡眠的运动性肌张力缺失和皮层电变化。我们记录了13只乌拉坦麻醉、自主呼吸、气管切开并切断迷走神经的大鼠的皮层和海马脑电图以及颏舌肌和吸气肋间肌活动。在脑电图活动为高电压/低频率的稳态期，将卡巴胆碱微量注射（15 - 40 nl，10 mM）注入脑桥内侧网状结构。在12只大鼠中，卡巴胆碱引发了颏舌肌典型的快速眼动睡眠刻板性肌张力缺失发作，但肋间肌活动未受影响，其潜伏期和持续时间分别为2.2±0.3分钟（平均值±标准误）和11.0±2.9分钟。在其中4只大鼠中，与快速眼动睡眠相似，颏舌肌活动的主要抑制（-74±9%）伴随着脑电图去同步化、海马θ节律的出现以及呼吸频率增加（+14±3%）。在其余8只大鼠中，颏舌肌活动的刻板性抑制（-48±3%）在没有脑电图去同步化和海马θ节律的情况下发生，并伴随着呼吸频率降低（-6±2%）；这是去大脑动物典型的反应模式。在同一只大鼠中，在相同解剖部位重复注射卡巴胆碱可获得类似的反应模式。脑桥注射阿托品可阻止对后续卡巴胆碱注射的反应。因此，在乌拉坦麻醉的大鼠中，脑桥注射卡巴胆碱始终能对咽部肌肉与呼吸泵肌肉活动产生差异性抑制，并且在一部分动物中，这还伴随着典型的快速眼动睡眠的皮层和海马电图变化。这表明在全身麻醉下，药理学方法可激活快速眼动睡眠的升、降信号所依赖的复杂且刻板的神经元事件。这种简化的实验准备可能有助于研究快速眼动睡眠产生的中枢神经元机制；尤其适用于那些在完整的自然睡眠动物中难以实施的技术研究。仅在卡巴胆碱诱导脑电图去同步化时观察到的呼吸频率加快表明，与皮层电变化相关的神经事件促成了自然快速眼动睡眠中观察到的呼吸频率增加。
