AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 5 812-R822, Copyright © 1988 by American Physiological Society

ARTICLES

Peak duration of serum melatonin and short-day responses in adult Siberian hamsters

T. J. Bartness and B. D. Goldman
Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.

Long photoperiod-housed, adult Siberian hamsters were pinealectomized and given daily subcutaneous infusions of melatonin (MEL) to determine which characteristic of the MEL secretion profile is critical for short photoperiod-induced physiological responses. Long-duration MEL infusions (10 or 12 h) given for 5 wk elicited short-day-type responses [i.e., decreased body, testes, and epididymal white adipose tissue (EPIWAT) weights, EPIWAT lipoprotein lipase activity, carcass lipid content, and serum follicle-stimulating hormone and prolactin levels]. In contrast, short- or intermediate-duration (5 or 8 h) MEL infusions or saline infusions were without effect. Long-duration MEL infusions elicited short-day-type responses independently of both the time of day when MEL was administered and of the MEL dose if the latter was greater than or equal to 6.25 ng MEL/daily infusion. The continuity of the 10-h MEL infusions was important for triggering short-day-type responses; 10-h MEL infusions interrupted at their midpoint by 2 h of no infusion were ineffective even though dose and total duration were held constant. The body and lipid mass decreases were independent of the gonads, since castrated and gonad-intact hamsters responded similarly to the daily 10-h MEL infusions. Decreased body weight resulting from long-duration MEL infusions were never accompanied by decreased food intake. We conclude that the peak nocturnal duration of MEL is the critical parameter of the MEL secretion profile for triggering short-day-induced responses in adult Siberian hamsters.

This article has been cited by other articles:

				T. J. Bartness, G. E. Demas, and C. K. Song Seasonal Changes in Adiposity: the Roles of the Photoperiod, Melatonin and Other Hormones, and Sympathetic Nervous System Experimental Biology and Medicine, June 1, 2002; 227(6): 363 - 376. [Abstract] [Full Text] [PDF]

				C. K. Song and T. J. Bartness CNS sympathetic outflow neurons to white fat that express MEL receptors may mediate seasonal adiposity Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2001; 281(2): R666 - R672. [Abstract] [Full Text] [PDF]

				D. A. Freeman and I. Zucker Refractoriness to melatonin occurs independently at multiple brain sites in Siberian hamsters PNAS, May 22, 2001; 98(11): 6447 - 6452. [Abstract] [Full Text] [PDF]