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  • Title: Distribution of gonadotropin releasing-hormone-II in the house sparrow brain (Passer domesticus).
    Author: Stevenson TJ, Arckens L, MacDougall-Shackleton SA.
    Journal: Gen Comp Endocrinol; 2007 Jan 01; 150(1):96-105. PubMed ID: 16959254.
    Abstract:
    In songbirds, three isoforms of gonadotropin-releasing hormone (GnRH) have been reported: chicken GnRH-I (GnRH-I); and -II (GnRH-II); and lamprey GnRH-III (lGnRH-III). In galliformes, the distribution of GnRH-I and -II have been extensively studied. GnRH-I cell bodies are located primarily in the preoptic-septal region and primarily project to the median eminence. GnRH-II cell bodies are located in the midbrain and project to various hypothalamic and extrahypothalamic regions. In songbirds, the distributions of only GnRH-I and lGnRH-III have been thoroughly described. Songbirds differ from galliformes in that they possess specialized neural regions for the learning and production of complex vocalizations, the song-control system. In songbirds lGnRH-III was found within many song nuclei. In this study, we investigated the distribution of GnRH-II in the male house sparrow (Passer domesticus) brain. Our objectives were (1) to determine the distribution of GnRH-II in the male songbird brain and (2) to investigate the presence of GnRH-II in song control nuclei. Our study identified immunoreactive magnocellular GnRH-II cell bodies in the oculomotor region of the mesencephalon and parvicellular cells in the lateral hypothalamus. Also, an extensive network of GnRH-II immunoreactive fibres was observed in hypothalamic nuclei and extrahypothalamic regions. Immunoreactive GnRH-II fibres were most abundant in the preoptic area, ventromedial nucleus, hippocampus and the medial septum. Sparse immunoreactivity was also observed in the mesencephalon and diencephalon. GnRH-II was not identified in any of the song-control nuclei. Unlike lGnRH-III, these data suggest that GnRH-II is not directly involved with song learning, perception or production.
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