Enhanced reproductive responses to melatonin in juvenile siberian
hamsters.
Prendergast, Brian J., Kimberly K. Kelly, Irving Zucker, and Michael
R. Gorman.
Departments of Psychology and Integrative Biology, University of
California, Berkeley, CA 94720, USA, Department of Psychology and
Michigan Society of Fellows, University of Michigan, Ann Arbor, MI
48109
APStracts 3:0169R, 1996.
Reproductive responses to melatonin (MEL) exposure were assessed in
male Siberian hamsters gestated in long (16 h light/day; 16L) or
short (8L) day lengths (DLs). Hamsters were maintained in constant
light beginning at 14 days of age (Day 14) and infused for 3
successive days beginning on Day 18, 25 or 32 with long (12 h/day) or
short (6 h/day) durations of melatonin (MEL) or saline (SAL). Two
weeks later testis and body weights were determined. Responsiveness
to MEL was enhanced in hamsters beginning shortly after weaning and
was influenced by photoperiodic history. Gonadal growth in 16L
hamsters was inhibited by 12 h MEL infusions initiated on Day 18 or
Day 25, but infusions initiated on Day 32 were ineffective. Hamsters
gestated in 8L were not responsive to MEL treatments initiated on Day
18, but discriminated 12 h from 6 h infusions at Day 25, and
manifested reduced gonadal growth after 12 h MEL infusions on Day 32.
Hamsters born in 8L to dams judged as photoinsensitive to short DLs
did not respond to 12 h infusions on Day 32 as inhibitory signals. We
propose that maternal MEL secretion provides juvenile males with a
photoperiodic history which allows them to compare gestational with
early postweaning MEL signals and thereby program seasonally
-appropriate developmental trajectories.
Received 8 December 1995; accepted in final form 20 April 1996.
APS Manuscript Number R774-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96