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Acute psychological stress has been previously shown to increase innate immune system activity in mature rats. However, the exact timecourse of innate immune
system activity in response to stressor challenge in these animals has not been well established. In addition, the effect of early life stress (ELS) on the response to
stress in mature rats has not been examined. Using enzyme-linked immunosorbent assays (ELISAs), the current study found that levels of interleukin (IL)-6 in the
circulation peaked at 90 minutes post-onset of footshock stress in rats without ELS experiences. Additionally, circulating levels of IL-1beta peaked at 30 minutes
after stress onset. IL-6 and IL-1beta protein levels in the hippocampus did not show definitive peaks after footshock stress. However, animals that underwent
surgery for intravenous jugular catheters showed elevated circulating and brain levels of IL-6 and IL-1beta at rest and after challenge with footshock. The results
of the current study were inconclusive with respect to the effect of ELS on stress-induced innate immune system function. Further studies should be conducted to
examine the effects of ELS on innate immune system responses to acute stress challenge. Interestingly, animals that underwent surgery for intravenous jugular
catheters displayed increased innate immune responses to stress relative to rats that did not undergo surgery.
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