Photoperiod and testosterone regulate androgen receptor immunostaining in the Siberian hamster brain.
Day length regulates the effects of gonadal steroids on gonadotropin secretion and behavior in seasonal breeders. To determine whether this influence of photoperiod results from changes in androgen receptor expression in Siberian hamster brain regions that regulate neuroendocrine function, androgen receptor immunostaining was examined in castrated animals given either no androgen replacement or one of three doses of testosterone (T) resulting in physiological serum concentrations. Half of the animals were housed under inhibitory photoperiod conditions, and immunostaining was quantified 11 days later. Measurement of serum gonadotropin and prolactin concentrations confirmed that androgen exerted graded effects on pituitary function but that the animals were killed before photoperiodic influences had fully developed. T significantly increased the numbers of androgen receptor-immunoreactive cells in every brain region examined. Photoperiod exerted no significant influence on androgen receptor-immunoreactive cell number in the arcuate nucleus, bed nucleus of the stria terminalis (BNST), medial preoptic nucleus, or in medial amygdala. An interaction between T and photoperiod was observed in the BNST and in the rostral and middle portions of the arcuate nucleus. Although increasing concentrations of T resulted in more intense cellular immunostaining in the BNST and arcuate, this effect was not influenced by day length. These results indicate that relatively short-duration (11 days) exposure to inhibitory photoperiod triggers localized and regionally specific changes in androgen receptor expression.
Department of Biology, Center for Neuroendocrine Studies, University of Massachusetts, Amherst, Massachusetts 01003, USA. elb@bio.umass.edu
Eric L
EL
Bittman
David A
DA
Ehrlich
Justyne L
JL
Ogdahl
Amy E
AE
Jetton
D000704:Analysis of Variance; D000818:Animals; D002369:Castration; D002940:Circadian Rhythm; D006224:Cricetinae; D005640:Follicle Stimulating Hormone / Q000097:blood; D007150:Immunohistochemistry; D008029:Lighting; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D009490:Neurosecretory Systems / Q000378:metabolism / Q000528:radiation effects; D017111:Phodopus; D017440:Photoperiod; D011388:Prolactin / Q000097:blood; D016548:Prosencephalon / Q000378:metabolism / Q000528:radiation effects*; D011944:Receptors, Androgen / Q000378:metabolism* / Q000528:radiation effects; D012098:Reproduction / Q000502:physiology; D013737:Testis / Q000502:physiology / Q000528:radiation effects*; D013739:Testosterone / Q000502:physiology*
D011944:Receptors, Androgen; D013739:Testosterone; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone