[Effects of electroacupuncture at different hours on leucine-enkephalin contents in rat brain regions].

In the present study, rats were synchronized with light from 8:00 to 20:00, then darkness. Water and food were available ad libitum. The basic levels in medulla oblongata plus pons, hypothalamus, hippocampus midbrain, striatum and cortex, and electroacupuncture influences on them were compared at four different times of a day (5:00, 11:00, 17:00 and 23:00). It was found that: (1) The basic level of LEK in the medulla oblongata plus pons at 11:00 was the highest among the four times; (2) The LEK content increased by 34.8% in the hypothalamus and decreased by 21.4% in the cortex when EA was given at 5:00; The LEK levels in the hypothalamus and the hippocampus increased by 65.3% and by 37.0% respectively when EA at 11:00. The LEK level in the hippocampus increased by 50.1% when EA at 17:00; The hippocampus decreased by 29.8% when EA at 23:00. The results show that a circadian rhythm was evident in the LEK level of the rat medulla oblongata plus pons, also EA at different hours produced different effects on LEK contents in rat discrete brain regions. This provides experimental evidence for acupuncture treatment selecting hours clinically. Also, the physiological circadian variation and the influence of time factor on acupuncture effects should be considered in study of acupuncture mechanism.