Meeting Abstract
Cold exposure, especially early in life, can be stressful. We investigated if early-life cold exposure (first two weeks post-hatch) affects hypothalamic-pituitary-adrenal (HPA) axis sensitivity and global DNA methylation in the brain of juvenile and adult male and female Australian zebra finches (Taenopygia gutta). Plasma corticosterone (Cort) levels after restraint was used to determine HPA axis sensitivity. Control birds showed the predicted elevation in plasma Cort after restraint stress in adulthood, however cold-exposed birds exhibited a blunted Cort response. The attenuated Cort response displayed by cold-exposed birds suggests that these birds are either maintaining higher baseline Cort levels to begin with or that they have an attenuated stress response. In adulthood, there was no significant difference in global DNA methylation levels between cold-exposed and control birds. Cold-exposed juveniles showed no significant difference between baseline and restraint plasma Cort levels, however these birds had significantly lower methylation levels. In parallel, we administered oral Cort for 10 days post hatch and measured global methylation patterns in juvenile and adult male finches to see if the similar results were observed. The results of both experiments were consistent, juvenile birds displayed a significant reduction in global DNA methylation but the adult birds did not. These studies suggest that hypomethylation on a global scale can occur after adverse early life events, however it is not known if these treatments resulted in hypermethylation of any specific gene sequences.
