Bartell Paul A, Miranda-Anaya Manuel, Menaker Michael
Forschungsstelle für Ornithologie der Max-Planck-Gesellschaft, Von-der-Tann-Strasse 7, D-82346 Erling-Andechs, Germany.
J Biol Rhythms. 2004 Feb;19(1):47-57. doi: 10.1177/0748730403261133.
The circadian system of the lizard Iguana iguana is composed of several independent pacemakers that work in concert: the pineal gland, retinae of the lateral eyes, and a fourth oscillator presumed to be located in the hypothalamus. These pacemakers govern the circadian expression of multiple behaviors and physiological processes, including rhythms in locomotor activity, endogenous body temperature, electroretinogram, and melatonin synthesis. The numerous, easily measurable rhythmic outputs make the iguana an ideal organism for examining the contributions of individual oscillators and their interactions in governing the expression of overt circadian rhythms. The authors have examined the effects of pinealectomy and enucleation on the endogenous body temperature rhythm (BTR) and locomotor activity rhythm (LAR) of juvenile iguanas at constant temperature both in LD cycles and in constant darkness (DD). They measured the periods (tau) of the circadian rhythms of LAR and BTR, the phase relationships between them in DD (psiAT), and the phase relationship between each rhythm and the light cycle (psiRL). Pinealectomy lengthened tau of locomotor activity in all animals tested and abolished the BTR in two-thirds of the animals. In those animals in which the BTR did persist following pinealectomy, tau lengthened to the same extent as that of locomotor activity. Pinealectomy also delayed the onset of activity with respect to its normal phase relationship with body temperature in DD. Enucleation alone had no significant effect on tau of LAR or BTR; however, after enucleation, BTR became 180 degrees out of phase from LAR in DD. After both pinealectomy and enucleation, 4 of 16 animals became arrhythmic in both activity and body temperature. Their data suggest that rhythmicity, period, and phase of overt circadian behaviors are regulated through the combined output of multiple endogenous circadian oscillators.
松果体、侧眼视网膜，以及一个推测位于下丘脑的第四振荡器。这些起搏器控制着多种行为和生理过程的昼夜表达，包括运动活动节律、内源性体温、视网膜电图和褪黑素合成。鬣蜥有众多易于测量的节律性输出，使其成为研究单个振荡器及其相互作用对明显昼夜节律表达的贡献的理想生物体。作者研究了松果体切除和摘除眼球对幼年鬣蜥在恒温条件下，在光暗周期（LD）和持续黑暗（DD）中的内源性体温节律（BTR）和运动活动节律（LAR）的影响。他们测量了LAR和BTR昼夜节律的周期（tau）、它们在DD中的相位关系（psiAT），以及每个节律与光周期的相位关系（psiRL）。松果体切除使所有受试动物的运动活动tau延长，并使三分之二的动物的BTR消失。在松果体切除后BTR仍持续存在的动物中，tau延长的程度与运动活动相同。松果体切除还使活动开始相对于其在DD中与体温的正常相位关系延迟。单独摘除眼球对LAR或BTR的tau没有显著影响；然而，摘除眼球后，在DD中BTR与LAR的相位相差180度。松果体切除和摘除眼球后，16只动物中有4只在活动和体温方面都变得无节律。他们的数据表明，明显的昼夜行为的节律性、周期和相位是通过多个内源性昼夜振荡器的联合输出进行调节的。
