Kim Juhyon, Nakajima Kazuki, Oomura Yutaka, Wayner Matthew J, Sasaki Kazuo
Division of Bio-Information Engineering, Faculty of Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan.
Peptides. 2009 Feb;30(2):191-209. doi: 10.1016/j.peptides.2008.09.023. Epub 2008 Oct 14.
Orexin-A (ORX-A) and orexin-B (ORX-B) play critical roles in the regulation of sleep-wakefulness and feeding. ORX neurons project to the pedunculopontine tegmental nucleus (PPT), which regulates waking and rapid eye movement (REM) sleep. Thus, we examined electrophysiological effects of ORXs on rat PPT neurons with a soma size of more than 30 microm. Whole cell patch clamp recording in vitro revealed that ORX-A and ORX-B depolarized PPT neurons dose-dependently in normal and/or tetrodotoxin containing artificial cerebrospinal fluids (ACSFs), and the EC(50) values for ORX-A and ORX-B were 66 nM and 536 nM, respectively. SB-334867, a selective inhibitor for ORX 1 (OX(1)) receptors, significantly suppressed the ORX-A-induced depolarization. The ORX-A-induced depolarization was reduced in high K(+) ACSF with extracellular K(+) concentration of 13.25 mM or N-methyl-d-glucamine (NMDG(+))-containing ACSF in which NaCl was replaced with NMDG-Cl, and abolished in high K(+)-NMDG(+) ACSF or in a combination of NMDG(+) ACSF and recordings with Cs(+)-containing pipettes. An inhibitor of Na(+)/Ca(2+) exchanger and chelating intracellular Ca(2+) had no effect on the depolarization. Most of PPT neurons studied were characterized by an A-current or both A-current and a low threshold Ca(2+) spike, and predominantly cholinergic. These results suggest that ORXs directly depolarize PPT neurons via OX(1) receptors and via a dual ionic mechanism including a decrease of K(+) conductances and an increase of non-selective cationic conductances, and support the notion that ORX neurons affect the activity of PPT neurons directly and/or indirectly to control sleep-wakefulness, especially REM sleep.
食欲素A（ORX-A）和食欲素B（ORX-B）在睡眠-觉醒和进食调节中发挥着关键作用。ORX神经元投射到脚桥被盖核（PPT），该核调节觉醒和快速眼动（REM）睡眠。因此，我们研究了食欲素对大鼠PPT神经元（胞体大小超过30微米）的电生理效应。体外全细胞膜片钳记录显示，在正常和/或含河豚毒素的人工脑脊液（ACSF）中，ORX-A和ORX-B使PPT神经元去极化呈剂量依赖性，ORX-A和ORX-B的半数有效浓度（EC50）值分别为66 nM和536 nM。SB-334867是一种选择性的食欲素1（OX1）受体抑制剂，可显著抑制ORX-A诱导的去极化。在细胞外钾离子浓度为13.25 mM的高钾ACSF或用N-甲基-D-葡萄糖胺（NMDG+）替代氯化钠的含NMDG+的ACSF中，ORX-A诱导的去极化减弱，而在高钾-NMDG+ACSF或NMDG+ACSF与含铯（Cs+）移液管记录的组合中则消失。钠/钙交换抑制剂和螯合细胞内钙对去极化无影响。大多数研究的PPT神经元具有A电流或同时具有A电流和低阈值钙尖峰，且主要为胆碱能。这些结果表明，食欲素通过OX1受体并通过包括钾离子电导降低和非选择性阳离子电导增加的双重离子机制直接使PPT神经元去极化，并支持食欲素神经元直接和/或间接影响PPT神经元活动以控制睡眠-觉醒，尤其是REM睡眠的观点。
