Cytokines, Monoamines and Behavior

Re: Stress, Learned Helplessness, and Brain Interleukin-1, Steven F. Maier

Astrid C.E. Linthorst

On Tue Dec 8, Hymie Anisman wrote
>Hi Steve and Linda
>Great poster! Like you and several others in this symposium (Shanks, Linthorst, Kusnecov, Dunn) we've taken the view that cytokine effects may be interpreted centrally as if they were stressors. Two comments.
>1. Is the similarity between cytokines and stressors a result of IL-1 producing sickness, which then induces stress-like effects, or do cytokines activate central processes independent of malaise experienced by the animal?
>2. While cytokines have many effects similar to those elicited by stressors, we found that IL-1 and stressor effects are distinguishable particularly and mesolimbic sites. For instance, the  increase of in vivo DA release induced by stressors within the nucleus accumbens are not marked in IL-1 treated rats, and in prefrontal cortex the effects of IL-1 are limited at best (although 5-HT alterations are evident and synergisms with airpuff stress do appear). In contrast to IL-1, LPS was found to provoke accumbal DA changes. The latter data suggest that attributes of LPS in addition to IL-1 activation (or synergisms/additive effects with other processes) are responsible for the DA variations. So, after this long bit of rambling, my questions are (a) if IL-1 is interpreted as a stressor, do you see this being limited to hypothalamic processes, or do you believe that limbic regions are involved as well, and (b) is IL-1 cognitively appraised as a stressor?

>Incidentally, if Astrid Linthorst or Adrian Dunn are reading this, do you have any views on this?

Answer by Astrid: I don't think that inflammation should be regarded as a stressor at the level of the hypothalamus only. In fact, neurotransmitter changes observed in higher brain structures during inflammation suggest that cognitive/affective processes may be involved as well. Cognitive processes may play an important role in the future coping strategies of organisms to inflammation/sickness.

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