Wang Y J, Wang S K
J Tradit Chin Med. 1989 Mar;9(1):53-6.
The basic level of methionin-enkephalin (MEK) in rat medulla oblongata plus pons was the highest at 05:00 o'clock and the lowest at 23:00. In both hypothalamus and striatum at 05:00 it was higher than at 11:00, 17:00 and 23:00. In both hippocampus and midbrain at 05:00 and 23:00 it was higher than those at 11:00 and 17:00. In the cortex it was higher at 05:00 than at 11:00 and 17:00. The basic level of leucine enkephalin (LEK) in the medulla oblongata plus pons was the highest at 11:00 and the lowest at 17:00 and 23:00. Electroacupuncture (EA) at 05:00 increased the MEK content in the medulla oblongata plus pons and the LEK level in the hypothalamus. It decreased the MEK content in the hypothalamus and the LEK level in the cortex; EA at 11:00 produced decreases of MEK concentrations in the medulla oblongata plus pons and the midbrain and increases of MEK content in the cortex, hypothalamus and striatum. At 17:00 it increased the MEK level in the hypothalamus and the LEK content in the hippocampus. At 23:00 it reduced the levels of MEK and LEK in the hippocampus. The results suggest that there are very marked circadian rhythms in the MEK basic levels of the six discrete brain regions observed and the LEK of the medulla oblongata plus pons; EA at different times produces different effects on brain MEK and LEK levels.
大鼠延髓加脑桥中甲硫氨酸脑啡肽（MEK）的基础水平在凌晨5点最高，在晚上11点最低。在凌晨5点时，下丘脑和纹状体中的MEK水平均高于上午11点、下午5点和晚上11点。在凌晨5点和晚上11点时，海马体和中脑中的MEK水平均高于上午11点和下午5点。在皮质中，凌晨5点时的MEK水平高于上午11点和下午5点。延髓加脑桥中亮氨酸脑啡肽（LEK）的基础水平在上午11点最高，在下午5点和晚上11点最低。凌晨5点进行电针（EA）可增加延髓加脑桥中的MEK含量以及下丘脑中的LEK水平。它会降低下丘脑中的MEK含量以及皮质中的LEK水平；上午11点进行电针会使延髓加脑桥和中脑中的MEK浓度降低，使皮质、下丘脑和纹状体中的MEK含量增加。下午5点时，它会增加下丘脑中的MEK水平以及海马体中的LEK含量。晚上11点时，它会降低海马体中MEK和LEK的水平。结果表明，所观察的六个离散脑区的MEK基础水平以及延髓加脑桥中的LEK存在非常明显的昼夜节律；不同时间进行电针会对脑内MEK和LEK水平产生不同影响。
