Wellman Laurie L, Fitzpatrick Mairen E, Machida Mayumi, Sanford Larry D
Sleep Research Laboratory, Department of Pathology and Anatomy, Eastern Virginia Medical School, P. O. Box 1980, Norfolk, VA, 23507, USA.
Exp Brain Res. 2014 May;232(5):1555-65. doi: 10.1007/s00221-014-3850-z. Epub 2014 Feb 12.
Fear conditioning [inescapable shock training (ST)] and fearful context re-exposure (CR) alone can produce significant fear indicated by increased freezing and reductions in subsequent rapid eye movement (REM) sleep. Damage to or inactivation of the basolateral nucleus of the amygdala (BLA) prior to or after ST or prior to CR generally has been found to attenuate freezing in the shock training context. However, no one has examined the impact of BLA inactivation on fear-induced changes in sleep. Here, we used the GABAA agonist, muscimol (MUS), to inactivate BLA prior to ST, the period when fear is learned, and assessed sleep after ST and sleep and freezing after two CR sessions. Wistar rats (n = 14) were implanted with electrodes for recording sleep and with cannulae aimed bilaterally into BLA. After recovery, the animals were habituated to the injection procedure (handling) over 2 consecutive days and baseline sleep following handling was recorded. On experimental day 1, the rats were injected (0.5 μl) into BLA with either MUS (1.0 μM; n = 7) or vehicle (distilled water, n = 7) 30 min prior to ST (20 footshocks, 0.8 mA, 0.5-s duration, 60-s interstimulus interval). On experimental days 7 and 21, the animals experienced CR (CR1 and CR2, respectively) alone. Electroencephalogram and electromyogram were recorded for 8 h on each day, and the recording was scored for non-rapid eye movement sleep, REM sleep, and wakefulness. Freezing was examined during CR1 and CR2. MUS microinjections into BLA prior to ST blocked the post-training reduction in REM sleep seen in vehicle-treated rats. Furthermore, in MUS-treated rats, REM sleep after CR1 and CR2 was at baseline levels and freezing was significantly attenuated. Thus, BLA inactivation prior to ST blocks the effects of footshock stress on sleep and reduces fear memory, as indicated by the lack of freezing and changes in sleep after CR. These data indicate that BLA is an important regulator of stress-induced alterations in sleep and an important site for forming fear memories that can alter sleep.
恐惧条件反射[不可逃避的电击训练（ST）]以及单独的恐惧情境再暴露（CR）会引发显著的恐惧，表现为僵立增加以及随后快速眼动（REM）睡眠减少。在ST之前或之后，或者在CR之前，杏仁核基底外侧核（BLA）受损或失活，通常会减弱电击训练情境中的僵立。然而，没有人研究过BLA失活对恐惧诱导的睡眠变化的影响。在此，我们使用GABAA激动剂蝇蕈醇（MUS）在ST之前（即学习恐惧的时期）使BLA失活，并在ST后评估睡眠，以及在两次CR后评估睡眠和僵立情况。将Wistar大鼠（n = 14）植入用于记录睡眠的电极以及双侧靶向BLA的套管。恢复后，动物连续2天适应注射程序（处理），并记录处理后的基线睡眠。在实验第1天，大鼠在ST（20次足部电击，0.8 mA，0.5秒持续时间，60秒刺激间隔）前30分钟向BLA注射（0.5 μl）MUS（1.0 μM；n = 7）或溶剂（蒸馏水，n = 7）。在实验第7天和第21天，动物分别单独经历CR（分别为CR1和CR2）。每天记录脑电图和肌电图8小时，并对记录进行非快速眼动睡眠、REM睡眠和觉醒评分。在CR1和CR2期间检查僵立情况。在ST之前向BLA微量注射MUS可阻断在接受溶剂处理的大鼠中观察到的训练后REM睡眠减少。此外，在接受MUS处理的大鼠中，CR1和CR2后的REM睡眠处于基线水平，僵立显著减弱。因此，在ST之前BLA失活可阻断足部电击应激对睡眠的影响，并减少恐惧记忆，这表现为CR后缺乏僵立以及睡眠变化。这些数据表明，BLA是应激诱导的睡眠改变的重要调节因子，也是形成可改变睡眠的恐惧记忆的重要部位。
