Meeting Abstract

P1.70  Thursday, Jan. 3  Long term phenotypic effects of elevated corticosterone during the larval period in the South African clawed frog, Xenopus laevis HU, F*; CRESPI, E.J.; DENVER, R.J.; University of Michigan; Vassar College; University of Michigan fanghu@umich.edu

The intrauterine environment experienced by the fetus can have profound, long-term consequences for health and disease. Studies in experimental animals point to stress hormones as mediators of early life experience on later phenotypic expression. However, relatively little is known about the mechanisms of stress hormone action, or the consequences of early life stress on physiology and behavior in species other than mammals. We investigated the effects of exposure to a stress level of corticosterone (CORT) during the tadpole stage on measures of performance, hypothalamo-pituitary-interrenal (HPI) axis activity, and neural gene expression in juvenile frogs. We exposed early prometamorphic tadpoles (NF stage 52-54) to 100 nM CORT or vehicle in the aquarium water for 5 or 10 days and then allowed them to develop until 2 months post-metamorphosis. Each of the CORT treatments caused significant reductions in body weight at metamorphosis. However, juvenile frogs that had been treated with CORT as tadpoles exhibited catch-up growth, reaching similar body sizes as control animals by 2 months post- metamorphosis. Mean basal plasma [CORT] was significantly higher in animals from the 10 d CORT treatment, and there was a trend towards elevated plasma CORT in the 5 d CORT group. Immunohistochemical analysis showed that CORT exposure as a tadpole significantly decreased the number of glucocorticoid receptor (GR) immunoreactive cells throughout the brain and pituitary gland of juvenile frogs. Taken together, our findings show that elevations in plasma CORT during the tadpole stage can cause permanent alterations of the HPI axis, which could have long term fitness consequences. (Supported by NSF grant IBN 0235401 to R.J.D.)