INCREASE IN THE LEVEL OF RETINAL MELATONIN AND PERSISTENCE OF ITS DIURNAL RHYTHM IN RATS AFTER PINEALECTOMY

in Journal of Endocrinology
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H. S. YU
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S. F. PANG
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P. L. TANG
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To study the short- and long-term effects of pinealectomy on the level of retinal melatonin, male rats adapted to a photoperiod of 12 h light: 12 h darkness (with lights on at 06.00 h) were pinealectomized. In the short-term experiment, the rats were decapitated 1 week after pinealectomy. In the long-term experiment, 1 month was allowed for recovery. Melatonin was extracted from retinae and quantified by radioimmunoassay. A diurnal rhythm of retinal melatonin was found to persist after pinealectomy in both experiments. An increase in retinal melatonin was demonstrated 1 month after pinealectomy, indicating a compensatory effect on melatonin in the retinae of pinealectomized rats. Thus, biosynthesis of melatonin in the retina may be modulated through a negative feedback system.

 

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