Meijer J H, Groos G A
Department of Physiology and Physiological Physics, University of Leiden, The Netherlands.
Brain Res Bull. 1988 Jan;20(1):89-96. doi: 10.1016/0361-9230(88)90012-3.
The suprachiasmatic nuclei (SCN) are a major pacemaker of circadian rhythms in mammals. The SCN receive a direct retinal projection and a second optic input via the ventral lateral geniculate nucleus (vLGN). Both visual pathways mediate the entrainment of circadian rhythms, whereas both the SCN and the vLGN receive serotonergic afferents from the raphe nuclei. We investigated the effects of microiontophoretically applied serotonin (5HT) on SCN and vLGN cells in normal rats and rats chronically treated with the 5HT reuptake blocker imipramine (IMI). In the SCN of both groups over 40% of all recorded cells (N = 80) responded to 5HT with a dose-dependent suppression of their spontaneous or glutamate-evoked discharge, while twenty percent were tonically light-responsive. Except for one cell with an inconsistent 5HT response, none of the visual SCN neurons were 5HT-sensitive. In the vLGN of normal and IMI-treated rats about 60% of the cells recorded (N = 42) were inhibited by 5HT. In IMI-treated rats a few cases of excitation by 5HT were encountered in the vLGN. Visual as well as non-visual vLGN cells were responsive to 5HT. Microiontophoretic application of IMI resulted in suppression of electrical activity in both brain regions and enhanced the response induced by 5HT. Chronic IMI-treatment produced a significant increase in the sensitivity of cells in the SCN and vLGN to iontophoresed 5HT, without affecting the relative magnitude of the inhibition. The recovery from 5HT-induced inhibition was slow in these animals. Interestingly, the spontaneous discharge rate of both 5HT-sensitive and 5HT-insensitive SCN and vLGN cells was significantly lower in the imipramine-treated group.(ABSTRACT TRUNCATED AT 250 WORDS)
视交叉上核（SCN）是哺乳动物昼夜节律的主要起搏器。SCN接收来自视网膜的直接投射以及经由腹侧外侧膝状核（vLGN）的第二条视觉输入。这两条视觉通路都介导昼夜节律的同步，而SCN和vLGN都接受来自中缝核的血清素能传入纤维。我们研究了微量离子导入血清素（5-羟色胺，5HT）对正常大鼠以及长期用5HT再摄取阻滞剂丙咪嗪（IMI）治疗的大鼠的SCN和vLGN细胞的影响。在两组大鼠的SCN中，超过40%的记录细胞（N = 80）对5HT有反应，其自发或谷氨酸诱发的放电受到剂量依赖性抑制，而20%的细胞具有紧张性光反应。除了一个对5HT反应不一致的细胞外，视觉SCN神经元均对5HT不敏感。在正常和IMI治疗大鼠的vLGN中，约60%的记录细胞（N = 42）被5HT抑制。在IMI治疗的大鼠中，vLGN出现了少数5HT兴奋的情况。视觉和非视觉vLGN细胞均对5HT有反应。微量离子导入IMI导致两个脑区的电活动受到抑制，并增强了5HT诱导的反应。长期IMI治疗使SCN和vLGN细胞对离子导入5HT的敏感性显著增加，但不影响抑制的相对幅度。这些动物从5HT诱导的抑制中恢复缓慢。有趣的是，在丙咪嗪治疗组中，对5HT敏感和不敏感的SCN和vLGN细胞的自发放电率均显著降低。（摘要截短于250字）
