Meeting Abstract

P3.125  Wednesday, Jan. 6  Intrinsic neurons contribute to CRF innervation of the anuran optic tectum LARSON, R.*; AHMED, N.; SHOUKFEH, O.; BULIN, S.; BERGFELD, N.; LUSTGARTEN, J.; CARR, J.A.; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock; Texas Tech Univ., Lubbock richard.larson@ttu.edu

The 41 amino acid peptide corticotropin-releasing factor inhibits visually guided feeding in anuran amphibians, but the targets for CRF action within sub-cortical visual pathways are unknown. We examined the distribution and origin of CRF immunoreactivity in the anuran optic tectum, a brain area at the interface of sensorimotor integration. CRF immunoreactive perikarya and fibers were observed in the optic tectum of three representative anuran amphibian species, the Texas toad Bufo speciosus, the South African clawed frog Xenopus laevis, and the Korean fire bellied toad Bombina orientalis. Intrinsic CRF-immunoreactive neurons were observed in tectal layer 8 in all species. These neurons were pyriform in shape, and had clearly stained projections directed laterally within layer 8 or directed vertically toward tectal layer 9. The optic tectum expressed mRNA for CRF, CRF R1 receptor, and urocortin-1. CRF was detected in toad optic tectum by radioimmunoassay, although tectal CRF content was considerably less than that of the hypothalamus and forebrain. The rank order for CRF content in toad brain as determined by radioimmunoassay was forebrain, hypothalamus > brainstem > optic tectum >> olfactory bulb. Unilateral eye ablation did not affect CRF content of the contra lateral optic tectum. We conclude that neurons in the anuran optic tectum express mRNA for CRF and CRF R1 and that CRF immunoreactivity in the optic tectum arises from intrinsic CRF neurons.