Rani S, Kumar V
Department of Zoology, University of Lucknow, 226 007, Lucknow, India.
Physiol Behav. 2000 May;69(3):277-83. doi: 10.1016/s0031-9384(99)00247-4.
We have investigated phasic response of the photoperiodic clock to wavelength (color) and intensity of light in the male redheaded bunting (Emberiza bruniceps). Two experiments were performed. Experiment I examined whether varying the wavelength and intensity of first (entraining, E) and/or second (inducing, I) light pulse will alter the effects of a skeleton photoperiod. Birds were subjected for a period of 6 weeks to skeleton photoschedules (6L:5D:1L:12D; 6 h E-light pulse, 1 h I-light pulse) containing either an E-pulse at 5 or 20 lx coupled with I-pulse at 100 lx, or an E-pulse at 100 lx, coupled with I-pulse at 5- or 20-lx intensity. Additional two groups that received both E- and I-pulses at 100 lx served as controls. All photoschedules were employed in two colors-white and red (654 nm). There was the wavelength- and intensity-dependent stimulation of the testis growth and development. Long wavelengths of light (red light) induced faster and greater gonadal response, but the effects were also intensity dependent. Experiment II tested whether in the photostimulated birds held on long photoperiods the change in wavelength and intensity of light hours in the morning (entraining period) or the evening (inducing period) will influence the maintenance of the photoperiodic sensitivity. Birds were subjected initially to a long photoperiod of 14L:10D (L = approximately 500 lx; D = 0 lx) and then after 3 weeks, a 4-h light period in the morning (zeitgeber time, zt, 0-4) or in the evening (zt 10-14) of 14 L was substituted with white, green (528 nm), or red (654 nm) light at approximately 20-lx intensity. One group maintained on 14L:10D and other exposed to 10L:14D served as controls. After another 7 weeks, all birds were subjected to 16L:8D for a further 4 weeks to test for their responsivity to long-day photostimulation as a consequence of exposure to different experimental photoperiods. Testes regrew under 16L:8D only in birds that were exposed to 10L:14D or to 14L:10D with a green light pulse. However, there was no effect of the timing (morning, evening) of the light pulse. Taken together, the results from both the experiments indicate that in the redheaded bunting (1) the photoperiodic clock responds differentially to different wavelengths (colors, spectra) and intensities of light, and (2) the effects of wavelength and intensity of light on the clock are phase dependent, and such phasic effects can be seen in skeleton photoperiods in which light is applied discretely at different circadian phases.
我们研究了雄性赤头鹀（Emberiza bruniceps）的光周期时钟对光的波长（颜色）和强度的阶段性反应。进行了两个实验。实验一探究了改变第一次（诱导，E）和/或第二次（诱导，I）光脉冲的波长和强度是否会改变骨架光周期的影响。鸟类接受为期6周的骨架光周期（6小时E光脉冲，1小时I光脉冲），其中E脉冲的强度为5勒克斯或20勒克斯，I脉冲的强度为100勒克斯，或者E脉冲的强度为100勒克斯，I脉冲的强度为5勒克斯或20勒克斯。另外两组接受的E脉冲和I脉冲强度均为100勒克斯，作为对照。所有光周期均采用两种颜色——白色和红色（654纳米）。睾丸的生长和发育存在波长和强度依赖性刺激。长波长的光（红光）诱导更快且更强的性腺反应，但这些效应也依赖于强度。实验二测试了在长光周期下接受光刺激的鸟类中，早晨（诱导期）或傍晚（诱导期）光照时间的波长和强度变化是否会影响光周期敏感性的维持。鸟类最初接受14小时光照：10小时黑暗（L = 约500勒克斯；D = 0勒克斯）的长光周期，3周后，在14小时光照的早晨（授时时间，zt，0 - 4）或傍晚（zt 10 - 14）的4小时光照期被强度约为20勒克斯的白色、绿色（528纳米）或红色（654纳米）光所取代。一组维持在14小时光照：10小时黑暗，另一组暴露于10小时光照：14小时黑暗作为对照。再过7周后，所有鸟类再接受4周的16小时光照：8小时黑暗，以测试它们因暴露于不同实验光周期而对长日照光刺激的反应性。只有暴露于10小时光照：14小时黑暗或接受绿光脉冲的14小时光照：10小时黑暗的鸟类，其睾丸在16小时光照：8小时黑暗下才会重新生长。然而，光脉冲的时间（早晨、傍晚）没有影响。综合来看，两个实验的结果表明，在赤头鹀中：（1）光周期时钟对不同波长（颜色、光谱）和强度的光有不同反应；（2）光的波长和强度对时钟的影响是相位依赖性的，并且这种阶段性效应可以在骨架光周期中看到，其中光在不同的昼夜节律相位离散施加。
