Comparison of Properties of Brainstem Cholinergic and Noradrenergic Neurons in Vivo and in Vitro

1)在脲烷麻醉大鼠的背外侧被盖核（LDT）细胞外记录到两种动作电位（峰），即“短峰”和“宽峰”，以峰的宽度区分明显。后者与蓝斑核（LC）的去甲肾上腺素能神经元或中缝背核（DR）的血清素能神经元产生的峰值非常相似。大多数突出到前脑部位的LDT神经元具有宽尖峰，这与解剖学证据表明，宽尖峰神经元是胆碱能的。2)在脑干体外切片制备中，可以记录到LDT神经元在细胞内的宽峰。（为了集中精力做下面的实验，我们不能再做这个实验了。）3)为了明确中桥质胆碱能神经元作为激活系统组成部分的功能作用，我们对头部无痛固定的未损伤大鼠LDT的单个神经元活动进行了记录，并与皮质脑电图和颈部肌电图一起进行了记录。部分LC和DR神经元的活动也被记录下来进行比较。大多数动物被剥夺了24小时的睡眠。只观察了产生宽尖峰的神经元，从以前的研究中已知是胆碱能或单胺能。用玻璃移液管微电极射出的波塔明天蓝色标记所记录的神经元的位置，并在NADPH脱氢酶组织化学处理的切片上特异性地染色胆碱能神经元。4)根据46个宽突神经元在觉醒（AW）、慢波睡眠（SWS）和似然睡眠（PS）时的放电速率，将它们分为4组：1)在觉醒（AW）时最活跃，在睡眠（PS）时沉默（其中一些神经元可能是血清素能而不是胆碱能，因为LC中的10个神经元和DR中的9个神经元基本上都是血清素能的）；ii)神经元在PS期间最活跃，在AW期间沉默；iii)与SWS相比，AW和PS期间的神经元同样更活跃；ii组和iii组的神经元是LDT的主要组成部分，每组约占LDT神经元的40%。在大多数神经元中，放电的变化先于脑电图的变化，但在从睡眠中醒来时除外。5)感觉刺激，如轻触尾巴或对面部吹气，只是在某些神经元处于较高警觉性时诱发放电状态，而在另一些神经元中，感觉刺激诱发了重复习惯的相反应。6)本研究和其他研究结果表明，1)LDT由与睡眠/觉醒（以及感觉反应）相关的具有异质性特征的胆碱能神经元组成，大多数胆碱能神经元在PS或PS和AW中表现出较高的活性；2)一些被盖胆碱能神经元在诱导和维持PS中起关键作用，而在与意识相关的上升激活中起次要作用。少

1) Two kinds of action potentials (spikes) were recorded extracellularly in the laterodorsal tegmental nucleus (LDT) of the rat anesthetized with urethane, that is "brief spikes" and "broad spikes" , distinguished clearly with width of spikes. The latter were very similar to spikes generated by noradrenergic neurons of the locus coeruleus (LC) or serotonergic neurons of the dorsal raphe nucleus (DR). The majority of LDT neurons projecting to the forebrain sites had broad spikes, which, with an anatomical evidence, suggests that the broad-spike neurons are cholinergic.2) The broad spikes could be recorded intracellularly from LDT neurons in in vitro slice preparation of the brainstem. (We could not perform this experiment further in order to concentrate our efforts in the below experiments.)3) To clarify functional roles of mesopontine cholinergic neurons as a component of an activating system, single neuronal activity in the LDT of undrugged rats, whose head was fixed painlessly, was r … More ecorded along with cortical EEG and neck EMG. Activity of some LC and DR neurons was also recorded for comparison. Most of animals had been sleep-deprived for 24 hours. Observation was made only on neurons generating broad spikes, known from previous studies to be cholinergic or monoaminergic. The position of recorded neurons was marked by pontamine sky blue ejected from the glass pipette microelectrode, and was identified on sections processed for NADPH diaphorase histochemistry which stained cholinergic neurons specifically.4) According to their firing rates during wakefulness (AW), slow wave sleep (SWS) and paradoxical sleep (PS), 46 broad-spike neurons in the LDT were classified into four groups : i) neurons most active during AW and silent during PS (some of these neurons might be serotonergic rather than cholinergic, as substantially all of 10 neurons in the LC and 9 neurons in the DR) ; ii) neurons most active during PS and silent during AW ; iii) neurons equally more active during AW and PS than SWS ; and iv) others mainly characterized by transiently facilitated activity at awaking and/or onset of PS. Neurons of groups ii and iii were the main constituent of the LDT, either group populating about 40% of the LDT neurons. In most neurons change in firing preceded EEG change, except at awaking from PS.5) Sensory stimulation such as light touch to the tail or air puff to the face simply induced a state of firing during higher vigilance levels in some neurons, while in others the sensory stimulation evoked phasic responses habituated by repetition.6) The results of the present and other studies suggest that i) the LDT is composed of cholinergic neurons with heterogenous characteristics in relation to sleep/wakefulness (and also to sensory responses), the majority displaying heightened activity in PS or in PS and AW, and ii) some tegmental cholinergic neurons play a pivotal role in induction and maintenance of PS, while having but a minor role in the ascending activation relevant to consciousness. Less