Duncan M J, Goldman B D
J Exp Zool. 1984 Apr;230(1):89-95. doi: 10.1002/jez.1402300112.
The Djungarian hamster exhibits an agouti pelage in the summer and a predominantly white pelage in the winter. This pelage color cycle is known to be regulated by the length of the daily photoperiod probably acting through the pineal gland, as is the seasonal cycle of reproductive function with which it is closely correlated ( Figala et al., '73; Hoffmann, ' 78b ). The possibility of a causal relationship between the decline in gonadal hormone secretion and the coat color change occurring in short photoperiod was examined. Gonadectomized and intact male and female hamsters were exposed to either long (16L:8D) or short ( 10L : 14D ) photoperiod for several months. Gonadectomy neither induced the change to the winter pelage color in long photoperiod-housed animals, nor prevented either the change to the winter pelage or the spontaneous return to summer pelage color in short photoperiod-housed animals. Chronic implants of testosterone in castrated males delayed and attenuated the short photoperiod-induced coat color change. Administration of ovine prolactin (100 micrograms/day) stimulated pigmentation in hamsters with the winter pelage, whereas administration of a alpha MSH (30 micrograms/day) was without effect. These results suggest that changes in pelage color may be regulated largely by changes in pituitary prolactin secretion and modified to some extent by changes in gonadal steroid hormone secretion.
黑线毛足鼠在夏季呈现出刺豚鼠毛色，而在冬季则主要为白色毛色。已知这种毛色周期可能是通过松果体受每日光照周期长度调节的，其与紧密相关的生殖功能季节性周期情况相同（菲加拉等人，1973年；霍夫曼，1978年b）。研究了性腺激素分泌下降与短光照周期中出现的毛色变化之间存在因果关系的可能性。将去势和未去势的雄性和雌性仓鼠暴露于长（16小时光照：8小时黑暗）或短（10小时光照：14小时黑暗）光照周期下数月。去势既未在长光照周期饲养的动物中诱导出向冬季毛色的变化，也未阻止短光照周期饲养的动物向冬季毛色的变化或自发恢复为夏季毛色。给去势雄性仓鼠长期植入睾酮会延迟并减弱短光照周期诱导的毛色变化。给具有冬季毛色的仓鼠注射绵羊催乳素（100微克/天）会刺激色素沉着，而注射α-促黑素细胞激素（30微克/天）则没有效果。这些结果表明，毛色变化可能主要由垂体催乳素分泌的变化调节，并在一定程度上受性腺类固醇激素分泌变化的影响。
