Summary
Pinealectomy of the iguanid lizardSceloporus occidentalis freerunning in either continuous illumination or continuous darkness typically causes changes in the period of the activity rhythm as well as changes in the amount of daily activity (α). Blinding also alters the period of the freerunning activity rhythm. Continuous long term administration of melatonin via subcutaneous capsules causes a significant lengthening of the period of the activity rhythm (as well as a decrease in α) of pinealectomized and/or blinded lizards showing that melatonin exerts its action at extrapineal and extraocular sites. However, the amount of lengthening induced by melatonin is significantly greater in pinealectomized lizards than in intact lizards. The results indicate that the pineal (and possibly the eyes) act as coupling devices or as the loci of circadian pacemakers within a multioscillator system. Melatonin may function as a chemical messenger between the pineal (or eyes) and the rest of the circadian system.
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Underwood, H. Circadian organization in the lizardSceloporus occidentalis: The effects of pinealectomy, blinding, and melatonin. J Comp Physiol B 141, 537–547 (1981). https://doi.org/10.1007/BF01101477
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DOI: https://doi.org/10.1007/BF01101477