Developmental changes in c-fos expression to an age-specific social stressor in infant rats.
Young rats become immobile when exposed to a potentially infanticidal adult male rat. Male-induced immobility declines during the preweaning period, paralleling the decrease in infanticidal threat. To investigate the neural substrates underlying the developmental change in immobility, male-induced expression of the immediate-early gene c-fos was assessed on postnatal days 7, 14 and 21. A huddle of three young rats was exposed to an adult male behind a screen. As control, three littermates were put in the testing chamber but not exposed to the male. On day 7, male exposed and control pups were immobile most of the time and c-fos expression did not differ between conditions. On day 14, rats in the presence of the male stopped ongoing behaviors and became immobile. They had significantly higher c-fos expression in the paraventricular nucleus of the hypothalamus, the amygdala, the periaqueductal gray, and the locus ceruleus. On day 21, the male-exposed rats that were immobile had elevated c-fos expression in a similar pattern as on day 14, however, different nuclei of the amygdala were activated. In contrast, male-exposed 21-day-old rats that showed control levels of immobility did not have elevated c-fos expression in these areas. These results demonstrate that male exposure induced c-fos expression in brain areas of young rats in an age-specific pattern. Some of the activated brain areas seem to have contributed to immobility. Differential activation of neuronal populations may underlie developmental changes in defensive immobility during early ontogeny.
Wiedenmayer
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Department of Psychiatry, Columbia University College of Physicians and Surgeons, 1051 Riverside Drive, Unit 40, New York, NY 10032, USA. cpw14@columbia.edu
Barr
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D000818:Animals; D000831:Animals, Newborn; D001143:Arousal / Q000502:physiology*; D001921:Brain / Q000254:growth & development*; D001931:Brain Mapping; D005239:Fear / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D012931:Social Environment
D016760:Proto-Oncogene Proteins c-fos