AHMED, Nafisa; SHOUKFEH, Omar M.; CARR, James A.; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock: Distribution of Corticotropin-releasing Hormone-like Immunoreactivity in the Brain of the Texas Toad, Bufo speciosus
We investigated the distribution of corticotropin-releasing hormone (CRH)-like immunoreactive (ir) neurons in the brain of adult male B. speciosus. Well-organized groups of CRH-ir cells were located in the preoptic nucleus/amygdala complex and within the magnocellular nucleus and ventral infundibulum of the hypothalamus. Scattered CRH-ir cells were observed in the mesencephalic tegmentum and brainstem. An extensive CRH-ir fiber network was observed in the preoptic nucleus/amygdala complex; numerous CRH-ir fibers were observed throughout the hypothalamus and mesencephalic tegmentum. Scattered and isolated CRH-ir fibers were observed in the pretectal area and in the superficial layers of the optic tectum. Dual immunostaining revealed co-localization of arginine vasotocin-ir and CRH-ir within the magnocellular hypothalamus but there was little evidence for co-existence of the two peptides within neurons. Our data indicate that CRH neurons have widespread projections to hypothalamic, limbic, and brainstem areas of the toad brain. The observation that CRH-ir neurons project to the tectum and dorsal thalamus indicates potential regulation of visuomotor pathways. Supported by a Howard Hughes Medical Institute grant through the Undergraduate Biological Sciences Education Program to Texas Tech University.