Zhou X J, Jiang X H, Yu G D, Yin Q Z
Laboratory of Neurobiology, Suzhou Medical College, Suzhou 215007, China.
Sheng Li Xue Bao. 2000 Jun;52(3):215-9.
Spontaneous firing of suprachiasmatic nucleus (SCN) neurons and the effect of melatonin (MEL) were examined in hypothalamic slices made from pinealectomized rats or from the rats exposed to constant light. The results are as follows. (1) Under normal light cycle (light dark=12 12), SCN neurons displayed a circadian rhythm in spontaneous discharges. A peak about 8.3 Hz was presented at CT (circadian time) 6 8 and a trough about 3.8 Hz at CT18 20. The circadian rhythm persisted after pinealectomy, but disappeared after constant light exposure. (2) The response of SCN neurons to MEL was mainly inhibitory. Under normal light exposure, the inhibitory proportion was higher during the subjective day with the largest proportion of about 42% at CT8 10, and was lower during the subjective night with the largest proportion of about 26% at CT22 24. Under both constant light exposure and pinealectomy, the circadian rhythm of the response of SCN neurons to MEL disappeared. (3) The inhibitory effect of MEL on spontaneous discharges of SCN neurons was blocked by ML-1 receptor antagonist luzindole, but not by ML-2 receptor antagonist prazosin. The above results suggest that pineal gland, as a regulator of the organization of circadian rhythm, regulates the circadian rhythm of SCN neurons at two responsive time windows (CT8 10 and CT22 24) through high affinity ML-1 receptors in SCN.
在松果体切除的大鼠或持续光照的大鼠制作的下丘脑切片中，检测了视交叉上核（SCN）神经元的自发放电以及褪黑素（MEL）的作用。结果如下：（1）在正常光照周期（光照∶黑暗 = 12∶12）下，SCN神经元的自发放电呈现昼夜节律。在昼夜时间（CT）6至8时出现约8.3 Hz的峰值，在CT18至20时出现约3.8 Hz的谷值。松果体切除后昼夜节律持续存在，但在持续光照后消失。（2）SCN神经元对MEL的反应主要是抑制性的。在正常光照下，主观白天的抑制比例较高，在CT8至10时最大比例约为42%，主观夜间的抑制比例较低，在CT22至24时最大比例约为26%。在持续光照和松果体切除两种情况下，SCN神经元对MEL反应的昼夜节律均消失。（3）MEL对SCN神经元自发放电的抑制作用被ML - 1受体拮抗剂鲁辛朵阻断，但未被ML - 2受体拮抗剂哌唑嗪阻断。上述结果表明，松果体作为昼夜节律组织的调节者，通过SCN中的高亲和力ML - 1受体在两个反应时间窗口（CT8至10和CT22至24）调节SCN神经元的昼夜节律。
