Goel N, Lee T M, Pieper D R
Department of Psychology, 525 East University, University of Michigan, Ann Arbor, MI 48109, USA.
Brain Res. 1998 May 11;792(2):229-36. doi: 10.1016/s0006-8993(98)00134-6.
The diurnal rodent, Octodon degus, exhibits robust sex differences in several circadian measures, including circadian period (tau) and reentrainment rates to photic and nonphotic (social) zeitgebers. The neural substrates underlying such physiological differences remain unknown. In female degus, olfactory bulbectomies (BX) inhibit socially-facilitated reentrainment, but do not alter photic reentrainment, entrained measures, or tau in constant darkness (DD). This experiment investigated the effects of BX in male degus on (i) photic reentrainment rates of circadian rhythms following a 6-h phase advance of the light-dark (LD) cycle; (ii) photic entrainment; (iii) tau of free-running activity rhythms in DD; and (iv) body weight, paired testis weight, and the reproductive hormones, testosterone, androstenedione and follicle stimulating hormone (FSH). BX significantly delayed photic reentrainment rates. They did not, however, modify tau, the phase of activity onset or offset, amplitude or duration (alpha) of the activity rhythm, mean daily locomotor activity levels, or body weight. FSH, testosterone and androstenedione were unaffected by BX, whereas paired testis weights were significantly greater in BX degus compared with shams. Thus, the olfactory bulbs influence photic reentrainment of circadian rhythms and modestly affect the reproductive axis in male degus. Our results suggest that the olfactory bulbs may be a neural source of observed sex differences in photic reentrainment in degus, and highlight interspecies variation in the olfactory bulbs' effects on entrained and free-running circadian rhythms and on reproduction.
昼行性啮齿动物八齿鼠（Octodon degus）在多种昼夜节律指标上表现出明显的性别差异，包括昼夜周期（tau）以及对光和非光（社交）授时因子的重新同步率。导致这种生理差异的神经基础尚不清楚。在雌性八齿鼠中，切除嗅球（BX）会抑制社交促进的重新同步，但不会改变光诱导的重新同步、同步化指标或在持续黑暗（DD）中的tau。本实验研究了切除雄性八齿鼠嗅球对以下方面的影响：（i）在明暗（LD）周期提前6小时后，昼夜节律的光诱导重新同步率；（ii）光同步化；（iii）DD中自由活动节律的tau；以及（iv）体重、双侧睾丸重量和生殖激素睾酮、雄烯二酮和促卵泡激素（FSH）。切除嗅球显著延迟了光诱导的重新同步率。然而，它们并未改变tau、活动开始或结束的相位、活动节律的振幅或持续时间（alpha）、平均每日运动活动水平或体重。FSH、睾酮和雄烯二酮不受切除嗅球的影响，而与假手术组相比，切除嗅球的八齿鼠双侧睾丸重量显著更大。因此，嗅球影响昼夜节律的光诱导重新同步，并对雄性八齿鼠的生殖轴有适度影响。我们的结果表明，嗅球可能是八齿鼠在光诱导重新同步中观察到的性别差异的神经来源，并突出了嗅球对同步化和自由运行昼夜节律以及对生殖的影响的种间差异。
