Immunological responses of astroglia in the rat brain under acute stress: interleukin 1 beta co-localized in astroglia.

In previous studies, we demonstrated that acute stress induces microglial activation, without inducing any inflammatory responses; however, the effect of acute stress on astroglia, another glial cell subtype in the brain, remains to be elucidated. We determined the effect of acute stress on astroglia, particularly in terms of morphological changes and inflammatory properties. In contrast to microglia, the morphology of astroglia was not altered following a 2-h period of acute stress. Interestingly, the number of astroglia immunoreactive to interleukin 1 beta (IL-1β) significantly increased in several brain regions including the hippocampus, hypothalamus, amygdala, and periaqueductal gray following the acute stress. Confocal microscopy revealed that IL-1β is exclusively co-localized in astroglia, and not in neurons or microglia. The present study demonstrates that exposing rats to acute stress increases IL-1β immunoreactivity in astroglia in specific regions of the brain, and the mechanism of astroglial response to acute stress clearly differs from that of microglial response. Thus, astroglia may play important roles in neuroimmunomodulation through IL-1β during times of acute stress.