| Early-weaned piglets show abnormal behaviors, aggression, and cognitive deficits. Therefore, it was hypothesized that early-weaned piglets experience aberrant expression of stress response genes in the frontal cortex (FC) and hippocampus (HP), brain areas involved with cognitive function and social behavior. The objective was to examine the effects of early and conventional weaning on gene expression in the FC and HP of piglets either socially isolated or kept with their littermates. Early (EW; n = 6) and conventionally-weaned (CW; n = 6) piglets were weaned at 10 and 21 days after birth, respectively. Non-weaned piglets of both age groups, 12 (NW; n = 6) and 23 (NW; n = 6) days, remained with their dams. Half of CW, EW, and NW animals were socially isolated for 15 minutes at 12 (EW) and 23 (CW) days of age, immediately before euthanasia. Brain areas were collected and RNA extracted. A porcine brain library cDNA microarray and quantitative real-time RT-PCR were used to measure the expression of stress-responsive genes. Social isolation suppressed gene expression in the frontal cortex of piglets at 12 and 23 days of age, while early weaning suppressed hippocampal gene expression. These results may help to elucidate some of the biological basis for cognitive deficits and behavioral changes previously reported in early-weaned piglets. |
