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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Ornis Scandinavica. . 1992. Immunocytochemical distribution of GnRH in the brain of adult and posthatching Great Tit Parus major and Ring Dove Streptopelia roseogrisea. -Ornis Scand. 23: 222-232.This paper describes the appearance of GnRH-like immunoreactivity in the brain of adult and posthatching Ring Doves and Great Tits, with the goal of understanding the ontogeny of the gonadal-pituitary axis. To this end, we compared the distribution of GnRH immunostaining in adults, with that of posthatching birds of each species.The results of the adult study indicate the presence of a major group of GnRH immunoreactive perikarya in olfactory bulb, olfactory tubercle, nucleus accumbens, septal-preoptic-hypothalamic region, in the area surrounding the palial commissure, lateral hypothalamus, tuberal hypothalamus (Great Tit only) and near oculomotor nuclei nIII and nIV. Overall, these results are in good agreement with previous studies of GnRH-like immunoreactivity in other avian species, with some variations, most notably in the hypothalamic region. A surprising finding of the posthatching material was the absence of GnRH-like immunoreactive neurons and fibers in the septal-preoptic-hypothalamic region in the early days following hatching. The number and size of GnRH-containing neurons increased steadily in the post-hatching period from days 4-21. Also noteworthy was the absence of immunoreactive fibers in the median eminence and tuberal hypothalamic region before day 21 posthatching, suggesting that the hypothalamic-pituitarygonadal axis may not be mature before this time in the altricial and semialtricial species studied here.

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