Circadian and circannual rhythms of melatonin in plasma of male white-tailed deer and the effect of oral administration of melatonin

✍ Scribed by Bubenik, G. A. ;Smith, P. S.

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 670 KB
• Volume: 241
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402410110

✦ Synopsis

Circadian levels of melatonin (M) were determined in plasma of four male white-tailed deer sampled hourly in September for 24 h via indwelling jugular catheter. Concentrations of M, detected by the radioimmunoassay rise with the onset of darkness, peak at 1.00 h (265 pg/ml) and then quickly decline to baseline levels (60 to 70 pg/ml) maintained during the scotophase. Orally administered M (5 mg, given at 13:OO h) induced a rapid elevation of plasma M (peak 980 pg/ml at 15:OO h) followed by a decline to baseline (100 pg/ml) reached at 22:OO h. The usual midscotophase peak was abolished by exogenous M administration. Seasonal midscotophase levels of M (determined in three samples taken 45 min apart between 23:OO and 1:00 h reach maximum in December (1530 pg/ml) followed by decline to minimum (69 to 90 pg/ml) observed between May and July. The data indicate that: 1) similarly to other mammals, deer exhibit peak levels of M during the dark phase; 2) 5 mg of M given orally caused a rapid elevation of M levels in blood followed by a depression of the normally present night-time peak; and 3) midscotophase levels of M exhibit very pronounced seasonal fluctuations which might be related to yearly cycles, such as the reproduction, hair molt, and antler growth.

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