Goel N, Governale M M, Jechura T J, Lee T M
Department of Psychology, 207 High Street, Judd Hall, Wesleyan University, Middletown, CT 06459, USA.
Brain Res. 2000 Sep 22;877(2):306-13. doi: 10.1016/s0006-8993(00)02696-2.
The intergeniculate leaflet (IGL) modulates photic and nonphotic entrainment of circadian rhythms in nocturnal species, but nothing is known about its role in diurnal species. We investigated the significance of the IGL for circadian rhythm function in the diurnal rodent, Octodon degus, by determining the effects of bilateral electrolytic IGL lesions (IGL(X)) on: (i) photic entrainment; (ii) reentrainment rates to photic cues following a 6-h phase advance of the light-dark (LD) cycle; (iii) reentrainment rates to nonphotic social and photic cues following a 6-h phase advance of the LD cycle; and (iv) the circadian period (tau) of the activity rhythm in constant darkness (DD). IGL(X) significantly lengthened the duration (alpha) of the entrained activity rhythm and produced a significantly earlier phase of activity onset under entrained (LD 12:12) conditions, but did not change phase of activity offset, rhythm amplitude or mean daily activity levels. IGL(X) failed to modify tau of free-running activity rhythms in DD or alter reentrainment rates of circadian rhythms to nonphotic social and photic cues or photic cues alone. Thus, the IGL modulates two parameters of photic entrainment, but is not necessary for reentrainment to either nonphotic social or photic cues. Our results contribute to the growing comparative database on the neural mechanisms controlling circadian rhythms and indicate that the role of the IGL varies across species with no apparent relationship between diurnality-nocturnality and circadian function.
膝间小叶（IGL）调节夜行性物种昼夜节律的光刺激和非光刺激同步，但对其在昼行性物种中的作用却一无所知。我们通过确定双侧电解性IGL损伤（IGL(X)）对以下方面的影响，研究了IGL对昼行性啮齿动物八齿鼠昼夜节律功能的重要性：（i）光刺激同步；（ii）在明暗（LD）周期提前6小时后对光刺激线索的重新同步率；（iii）在LD周期提前6小时后对非光刺激社交和光刺激线索的重新同步率；以及（iv）在持续黑暗（DD）中活动节律的昼夜周期（tau）。IGL(X)显著延长了同步活动节律的持续时间（α），并在同步（LD 12:12）条件下使活动开始阶段显著提前，但未改变活动结束阶段、节律幅度或平均每日活动水平。IGL(X)未能改变DD中自由活动节律的tau，也未改变昼夜节律对非光刺激社交和光刺激线索或仅对光刺激线索的重新同步率。因此，IGL调节光刺激同步的两个参数，但对重新同步到非光刺激社交或光刺激线索并非必需。我们的结果有助于增加关于控制昼夜节律神经机制的比较数据库，并表明IGL的作用因物种而异，昼夜性与昼夜节律功能之间没有明显关系。
