Effects of photoperiod and androgen on pituitary function and
neuropeptide staining in siberian hamsters.
Bittman, Eric L., Amy E. Jetton, Constanza Villalba, and Geert J.
Devries.
DEPARTMENTS OF BIOLOGY AND PSYCHOLOGY AND PROGRAM IN NEUROSCIENCE
AND BEHAVIOR, UNIVERSITY OF MASSACHUSETTS, AMHERST MA 01003, PRESENT
ADDRESS: DEPARTMENT OF BIOLOGY, MIDDLE TENNESSEE STATE UNIVERSITY,
MURFREESBORO, TN 37132
APStracts 3:0049R, 1996.
Short photoperiods decrease gonadotropin secretion in Siberian
hamsters, but it is unknown whether the negative feedback effects of
androgens are amplified under such conditions as is the case in other
species. Photoperiod regulates the synthesis and secretion of GnRH,
-endorphin, and arginine vasopressin (AVP), which influence
gonadotropin release and sexual behavior but are themselves regulated
by gonadal steroid hormones. In order to determine the role of
androgen in these effects of daylength, immunostaining and
gonadotropin concentrations were examined after 8 weeks of exposure
to long or short days (LD or SD). Animals were either left intact,
castrated, or castrated with immediate or delayed replacement of
testosterone (T). We also investigated effects of age on
photoperiodic influences upon brain peptides and serum hormone
levels.
Received 12 October 1995; accepted in final form 30 January 1996.
APS Manuscript Number R648-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 14 February 96