Increase in the level of retinal melatonin and persistence of its diurnal rhythm in rats after pinealectomy.
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 pinealectomy. In the short-term experiment, the rats were decapitated 1 week after pinealectomized. 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.
D000818:Animals; D002940:Circadian Rhythm; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D010870:Pineal Gland / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012160:Retina / Q000378:metabolism*
D008550:Melatonin