Pineal Hydroxyindole-O-Methyltransferase (HIOMT) Activity in Female Japanese Quail (Coturnix coturnix japonica)

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Abstract
Pineal hydroxyindole-O-mefhyltransferase (HIOMT) activity was measured in female Coturnix throughout maturation and under different photoperiodic conditions. Since HIOMT has been found to O-methylate both serotonin and N-acetyl-serotonin to form 5-methoxytryptamine (5-MT) and melatonin, respectively, both substrates were used in assaying HIOMT in individual pineal glands. Pineal concentrations of melatonin synthesizing activity increaseed between 25 and 30 days and decreased between 30 days of age and the onset of lay, in female Coturnix on l6L:8D. The pineal concentration of 5-MT synthesizing activity did not change significantly during sexual maturation. Melatonin but not 5-MT synthesizing activity was found to be greater in females maturing on 16L:8D than on 8L:16D. Melatonin but not 5-MT synthesizing activity was decreased in mature females exposed to continuous darkness for 5 days. Because changes in melatonin and 5-MT synthesizing activities differed during sexual maturation and in response to long and short photoperiods, it appears that these two activities are regulated independently.
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