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- Title
Interactions of Testosterone and Short-Photoperiod Exposure on the Neuroendocrine Axis of the Male Syrian Hamster.
- Authors
Steger, Richard W.; Matt, Kathleen S.; Bartke, Andrzej
- Abstract
Exposure of adult male golden hamsters to short days (< 12.5 h light/day) leads to suppression of gonadal function which is secondary to reductions in gonadotropin and prolactin (PRL) secretion. Short-day (SD) exposure also leads to a reduction in hypothalamic norepinephrine (NE) and dopamine (DA) metabolism and an increase in hypothalamic LHRH content which appears to be related to a decrease in LHRH release. To determine whether SD-induced changes in NE and DA metabolism are dependent or independent of changes in circulating testosterone (T) levels and thus possible mediators of photoperiod effects on gonadotropin secretion, the effects of castration and steroid replacement on hypothalamic amine metabolism were studied in male hamsters maintained under long or short photoperiod conditions. The presence of Silastic® T-implants resulted in a greater suppression of LH and FSH in SD than in long-day (LD) hamster, but increased median eminence (ME) LHRH content in both groups. Exposure of castrate hamsters to short days led to a reduction of NE turnover in the ME and medial preoptic-suprachiasmatic area (MPOA) and a decrease in serum FSH levels. LH levels tended to be lower, but not significantly so. The decrease in ME NE turnover was potentiated by T replacement, but in the MPOA-SCN, T-implants reversed the effects of short days. NE turnover in the MBH was reduced by T in both LD and SD animals, but the effect was much greater in the SD animals. SD exposure also caused a decrease in ME DA metabolism that was reversed by T replacement. From these data, we suggest that many of the effects of photoperiod on hypothalamic LHRH and neurotransmitter metabolism are independent of its effects on serum T levels, which supports the hypothesis that SD-induced changes in gonadotropin secretion are secondary to changes in neurotransmitter metabolism. Copyright © 1986 S. Karger AG, Basel
- Publication
Neuroendocrinology, 1986, Vol 43, Issue 1, p69
- ISSN
0028-3835
- Publication type
Article
- DOI
10.1159/000124511