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Previous Article | Next Article
The Journal of Neuroscience, February 1, 1998, 18(3):1105-1114
Multioscillatory Circadian Organization in a Vertebrate, Iguana iguana
Gianluca Tosini and Michael Menaker Department of Biology and National Science Foundation Center for Biological Timing, Gilmer Hall, University of Virginia, Charlottesville, Virginia 22903
The lizard Iguana iguana when kept in constant ambient temperature displays endogenously generated circadian rhythms of body temperature and locomotor activity. Although surgical removal of the parietal eye has only slight effects on overt circadian rhythmicity, subsequent pinealectomy completely abolishes the rhythm of body temperature. However, the rhythm of locomotor activity is only slightly affected by parietalectomy plus pinealectomy. Our results demonstrate that the pineal complex is centrally involved in the generation and control of the circadian rhythm of body temperature but is only marginally involved in locomotor rhythmicity. Plasma melatonin levels are not significantly reduced by parietalectomy, whereas pinealectomy dramatically lowers the level and completely eliminates the circadian rhythm of melatonin in the circulation. Isolated parietal eye, pineal, and retina all synthesize melatonin with robust circadian rhythmicity when maintained for
4 d in culture, although in the intact animal all or almost all of the circulating melatonin comes from the pineal. The circadian system of I. iguana is composed of multiple circadian oscillators that reside in different tissues and have specific and different roles.
Key words: circadian rhythms; body temperature; locomotor activity; lizards; melatonin; pineal; parietal eye; retina
Copyright © 1998 Society for Neuroscience 0270-6474/98/1831105-10$05.00/0
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