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Effects of chronic melatonin administration on adrenal medulla catecholamine metabolism in adult male golden hamsters
Author(s) -
Esquifino Ana I.,
Moreno Maria L.,
Steger Richard W.
Publication year - 1994
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1994.tb00095.x
Subject(s) - melatonin , endocrinology , medicine , adrenal medulla , catecholamine , golden hamster , circadian rhythm , morning , hamster , epinephrine , biology
Esquifino AI, Moreno ML, Steger RW. Effects of chronic melatonin administration or adrenal medulla catecholamine metabolism in adult male golden hamsters. J. Pineal Res. 1994; 16: 154–158. Abstract The role of melatonin on adrenal medullary function was evaluated in adult golden (Syrian) hamsters injected daily at either 0800 or 1600 with melatonin (25 μxg/hamster) or vehicle (0. 1% ethanol in saline). Sixty days after initiation of treatment and 16 or 24 hr after the last injection of melatonin, animals were killed by decapitation and blood and tissue collected. Plasma prolactin levels were reduced by chronic administration of melatonin only when animals were treated at 1600. Tyrosine hydroxylase (TH) activity in the adrenal medulla was not changed by either morning or afternoon administration of melatonin. Phenylethanolamine‐N‐methyl transferase (PNMT) was changed by afternoon administration of melatonin. Morning and afternoon melatonin injections led to the reduction of both adrenal monoamine oxidase (MAO) and catechol‐O‐methyl transferase (COMT) activities although the afternoon injections led to a greater magnitude of change. Norepinephrine and epinephrine contents were significantly reduced by morning melatonin administration but were not changed by afternoon administration of the hormone. These data suggest that melatonin has direct and possibly indirect effects on adrenal medullary function in the hamster. However, further studies will be required to characterize the effects of melatonin on catecholamine synthesis and release and the physiological significance of these effects.