Morin L P, Blanchard J
Department of Psychiatry and Behavioral Science, State University of New York, Stony Brook 11794.
Brain Res. 1991 Dec 6;566(1-2):173-85. doi: 10.1016/0006-8993(91)91696-x.
The midbrain raphe complex innervates the circadian rhythm regulating system by direct projections to the suprachiasmatic nucleus (SCN) and the intergeniculate leaflet (IGL). The present experiments examined the changes in circadian rhythm regulation consequent to the depletion of brain serotonin by central 5,7-dihydroxytryptamine (DHT) application. Adult male hamsters with access to running wheels were entrained to a light-dark cycle 14:10 (LD) of photoperiod, pre-treated with desmethylimipramine and given bilateral lateral ventricle infusions of 75 micrograms DHT/2.5 microliters 0.5% ascorbic acid in saline or vehicle only. Two separate experiments were performed. Four weeks after surgery, animals were transferred to either constant light (LL; Experiment 1) or constant dark (DD; Experiment 2). Animals remained in LL for 85 days, then were transferred to DD for 50 days, followed by a return to LD 14:10 for 14 days. Animals in Expt. 2 remained in DD for 55 days, were given 3 days food deprivation, then, beginning 35 days later, were periodically exposed to 30 min light pulses as a phase response curve (PRC) to light was generated. DHT treatment induced rapid appearance of advanced activity onset, delayed offset and longer duration of the nocturnal activity phase. DHT animals in LL had circadian locomotor rhythms much longer than control animals (24.43 +/- 0.04 vs 24.19 +/- 0.05 h) and normal circadian rhythmicity was rapidly lost by DHT animals in LL. There was no effect of DHT on circadian period in DD, but the DHT treated animals in DD had a larger phase delay region of the PRC than did controls and this was associated with an overall change in the temporal properties of the PRC. Serotonin immunohistochemistry showed an approximate 90% loss of cells from the dorsal raphe nucleus and decreased density of the serotonergic terminal field in the SCN and IGL. The results support the view that the serotonergic system modulates the phasic actions of light on the hamster circadian rhythm system. The data also indicate that hamsters can have a Type 0 PRC.
中脑缝际复合体通过直接投射到视交叉上核（SCN）和间膝叶（IGL）来支配昼夜节律调节系统。本实验研究了通过向中枢应用5,7 - 二羟基色胺（DHT）使脑内5 - 羟色胺耗竭后昼夜节律调节的变化。成年雄性仓鼠可使用跑轮，使其适应14:10光周期的明暗循环（LD），先用去甲丙咪嗪预处理，然后双侧侧脑室注射75微克DHT/2.5微升0.5%的抗坏血酸钠盐水溶液或仅注射溶剂。进行了两个独立的实验。手术后四周，将动物转移到持续光照（LL；实验1）或持续黑暗（DD；实验2）环境中。实验1中的动物在LL环境中饲养85天，然后转移到DD环境中50天，接着再回到14:10的LD环境中14天。实验2中的动物在DD环境中饲养55天，给予3天食物剥夺，然后在35天后开始，定期给予30分钟的光脉冲，以生成对光的相位反应曲线（PRC）。DHT处理导致活动开始提前、结束延迟以及夜间活动期持续时间延长的快速出现。LL环境中的DHT处理动物的昼夜运动节律比对照动物长得多（24.43±0.04小时对24.19±0.05小时），且LL环境中的DHT处理动物迅速失去正常的昼夜节律性。DHT对DD环境中的昼夜周期没有影响，但DD环境中DHT处理的动物的PRC的相位延迟区域比对照动物大，这与PRC的时间特性的总体变化有关。5 - 羟色胺免疫组织化学显示中缝背核细胞损失约90%，SCN和IGL中5 - 羟色胺能终末场密度降低。结果支持5 - 羟色胺能系统调节光对仓鼠昼夜节律系统的相位作用这一观点。数据还表明仓鼠可以有0型PRC。
