Lesions of the melatonin- and androgen-responsive tissue of the dorsomedial nucleus of the hypothalamus block the gonadal response of male syrian hamsters to programmed infusions of melatonin

被引:96
作者
Maywood, ES [1 ]
Bittman, EL [1 ]
Hastings, MH [1 ]
机构
[1] UNIV MASSACHUSETTS, DEPT BIOL, AMHERST, MA 01003 USA
基金
英国惠康基金;
关键词
D O I
10.1095/biolreprod54.2.470
中图分类号
Q [生物科学];
学科分类号
07 ; 0710 ; 09 ;
摘要
The objective of this study was to characterize a site at which it is likely that melatonin mediates photoperiodic control of reproduction in the male Syrian hamster. The first experiment was a comparison of the distributions of iodomelatonin (IMEL)-binding sites and cells immunoreactive to androgen receptors (AR-ir) in the medio-basal hypothalamus (MBH). AR-ir cells extended throughout the MBH, whereas IMEL binding was restricted to the dorsomedial nucleus (DMN). Comparisons between IMEL binding and AR-ir on adjacent cryostat sections revealed a clear overlap between the IMEL-binding sites and a distinct subpopulation of AR-ir cells within the DMN. The second experiment examined whether lesions of these IMEL- and androgen-responsive cells affected the response of the hamsters to short-day (SD)-like infusions of melatonin. Animals received sham or bilateral electrolytic lesions of the IMEL-binding sites within the DMN of the hypothalamus (MBH-X). Animals were pinealectomized and 4 wk later fitted with an s.c. cannula for the daily infusion of either melatonin (50 ng/h) or saline (500 mu l/10 h). After 6 wk the animals with sham lesions showed gonadal atrophy and lower serum concentrations of LH and prolactin (PRL) after infusions with melatonin. In contrast, MBH-X animals given melatonin had large testes and long-day (LD)-like serum LH concentrations. Infusions of melatonin did, however, cause a significant decline in serum PRL levels. This study shows that: an intact MBH is essential for the expression of gonadotrophic but not lactotrophic responses to melatonin and/or photoperiod. It also suggests that cells responsive to both gonadal steroids and melatonin may be involved in the seasonal variation in GnRH release, and indicates a site at which melatonin might influence sensitivity to steroid feedback, a hypothalamic function known to be regulated by photoperiod.
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页码:470 / 477
页数:8
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