title: Hormonal regulation of the annual pelage color cycle in the Djungarian hamster, Phodopus sungorus. II. Role of prolactin.
abstract: This study investigated whether photoperiod-induced changes in circulating prolactin levels, which have been observed in the Djungarian hamster ( Yellon and Goldman, '83; Duncan and Goldman, ' 83a ), might be involved in seasonal pelage color changes in this species. Injection of ovine prolactin (100 micrograms/day) inhibited the short photoperiod-induced winter molt. This finding indicated that the suppression of endogenous prolactin levels normally occurring in short photoperiod-housed hamsters (Duncan and Goldman, ' 83a ) may induce the winter molt. Suppression of prolactin secretion with bromoergocryptine (200 micrograms/day) strongly inhibited the spring molt, while concomitant treatment with ovine prolactin (100 micrograms/day) overcame this effect of bromoergocryptine. Injection of bromoergocryptine (200 micrograms/day) stimulated the winter molt in castrated hamsters housed in long photoperiod; concomitant injection of prolactin (100 micrograms/day) reversed this effect as well. These findings strongly suggested that an increase in endogenous prolactin levels may be necessary for the development and maintenance of the summer pelage.
mesh_terms: D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D006224:Cricetinae / Q000502:physiology*; D005260:Female; D006200:Hair Color / Q000187:drug effects; D008029:Lighting; D008297:Male; D011388:Prolactin / Q000494:pharmacology / Q000502:physiology*; D012621:Seasons
chemical_list: D001971:Bromocriptine; D011388:Prolactin