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先用持续光照和松果腺切除预处理大鼠 ,然后制成下丘脑薄片 ,记录其视交叉上核 (SCN)神经元的自发放电 ,观察其昼夜变化和褪黑素 (MEL)对它的影响。实验结果表明 :(1)在正常光照 (光照∶黑暗 =12∶12 )条件下 ,SCN神经元自发放电频率呈现昼高夜低的节律性。在昼夜时间 (CT) 6～ 8出现放电高峰 ,频率约为 8 3Hz ;在CT18～ 2 0出现低谷 ,频率约为 3 8Hz。松果腺切除后 ,SCN神经元自发放电的昼夜节律性基本保持 ,但在持续光照条件下 ,昼夜节律基本消失。 (2 )SCN神经元对MEL反应以抑制为主。在正常光照条件下 ,在白昼SCN神经元对MEL反应性较高 ,最大抑制率在CT8～ 10 ,约为 42 % ;在黑夜较低 ,最大抑制率在CT2 2～ 2 4,约为 2 6 %。在持续光照和松果腺切除条件下 ,SCN神经元都失去对MEL反应的昼夜节律性 ,且反应性增高。 (3)ML 1受体拮抗剂luzindole能阻断由MEL引起的SCN神经元自发放电抑制 ,而ML 2受体拮抗剂哌唑嗪却不能阻断。实验结果提示 ,松果腺作为大鼠昼夜节律组构的一个调整器 ,通过MEL作用于SCN中的高亲和性ML 1受体 ,在反应的两个时间窗口 (CT8～ 10和CT2 2～ 2 4)调节SCN的昼夜节律活动。
The rats were pretreated with continuous light and pineal gland resection, then the hypothalamic slices were made and the spontaneous discharges of the suprachiasmatic nucleus (SCN) neurons were recorded. The changes of diurnal changes and melatonin (MEL) influences. The experimental results show that: (1) Under normal light conditions (light: darkness = 12:12), spontaneous firing frequency of SCN neurons presents rhythm of daytime, night and low night. The discharge peak appeared at 6 ~ 8 at daytime and night time (CT), the frequency was about 8 3 Hz; at the trough of CT 18 ~ 20, the frequency was about 38 Hz. After excision of the pineal gland, the circadian rhythms of SCN neurons spontaneous discharge were basically maintained, but the circadian rhythm disappeared under the continuous illumination. (2) SCN neurons suppressed MEL reaction mainly. Under normal light conditions, SCN neurons were more responsive to MEL during daytime and the maximum inhibition rate was about 42% at CT8 ~ 10; at night was lower, the maximum inhibition rate was at CT2 2 ~ 2 4, which was about 26 %. Under continuous light and pineal excision, circadian rhythms of SCN neurons were lost and their reactivity was increased. (3) The luzindole, an ML 1 receptor antagonist, blocked the spontaneous inhibition of SCN neurons induced by MEL, whereas the ML 2 receptor antagonist prazosin did not block it. The experimental results suggest that pineal gland, as a regulator of circadian rhythms in rats, can act on high-affinity ML1 receptors in SCN via MEL. During the two reaction time windows (CT8-10 and CT2-2 ~ 2 4) Adjust circadian activity of SCN.