Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9113084 | General and Comparative Endocrinology | 2005 | 7 Pages |
Abstract
Vertebrates exhibit several forms of gonadotropin-releasing hormone (GnRH). In birds, chicken GnRH-I (cGnRH-I) is the primary hypophysiotropic form that regulates the hypothalamo-pituitary-gonad (HPG) axis. In seasonally breeding songbirds, cGnRH-I immunoreactivity is primarily in the preoptic septo-infidibular regions and varies greatly between the breeding and non-breeding season. Chicken GnRH-II (cGnRH-II) is more widely distributed throughout the avian brain, but cGnRH-II immunoreactivity has been found in the median eminence of quail. Thus, cGnRH-II may function in addition to cGnRH-I in the regulation of the HPG axis. If so, we predicted that cGnRH-II immunoreactivity should exhibit seasonal and age related variation similar to that observed for cGnRH-I. In this study, we compared hypothalamic immunoreactivity of cGnRH-I and -II (ir-cGnRH-I and ir-cGnRH-II) between breeding and non-breeding adult and juvenile house sparrows (Passer domesticus). We used immunocytochemistry with highly specific antibodies developed for quail to examine brains of free-living house sparrows collected in the breeding and non-breeding season. Results showed a greater number of ir-cGnRH-I cell bodies and beaded fibres in breeding adult birds compared to non-breeding adult and juvenile birds. Moreover, there were significantly more ir-cGnRH-II fibres in the preoptic area of breeding adult birds compared to non-breeding adult and juvenile birds. These data suggest that cGnRH-II undergoes seasonal- and age-related changes similar to cGnRH-I and implicate a role in regulating reproduction.
Related Topics
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Biochemistry, Genetics and Molecular Biology
Endocrinology
Authors
Tyler J. Stevenson, Scott A. MacDougall-Shackleton,