Abstract
Interleukin (IL)-6 has been proposed to mediate several sickness responses, including brain-mediated neuroendocrine, temperature, and behavioral changes. However, the exact mechanisms and sites of action of IL- 6 are still poorly understood. In the present study, we describe the effects of central administration of species-homologous recombinant rat IL-6 (rrIL- 6) on the induction of hypothalamic-pituitary-adrenal (HPA) activity, fever, social investigatory behavior, and immobility. After intracerebroventricular administration of rrIL-6 (50 or 100 ng/rat), rats demonstrated HPA and febrile responses. In contrast, rrIL-6 alone did not induce changes in social investigatory and locomotor behavior at doses of up to 400 ng/rat. Coadministration of rrIL-6 (100 ng/rat) and rrIL-1β (40 ng/rat), which alone did not affect the behavioral responses, reduced social investigatory behavior and increased the duration of immobility. Compared with rhIL-6, intracerebroventricular administration of rrIL-6 (100 ng/rat) induced higher HPA responses and early-phase febrile responses. This is consistent with a higher potency of rrIL-6, compared with rhIL-6, in the murine B9 bioassay. We conclude that species-homologous rrIL-6 alone can act in the brain to induce HPA and febrile responses, whereas it only reduces social investigatory behavior and locomotor activity in the presence of IL-1β.
Original language | English |
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Pages (from-to) | R652-R658 |
Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
Volume | 276 |
Issue number | 3 45-3 |
DOIs | |
Publication status | Published - Mar 1999 |
Keywords
- Adrenocorticotropic hormone
- Brain
- Corticosterone
- Hypothalamic-pituitary-adrenal activation
- Interleukin- 6
- Interleukin-1β
- Locomotor behavior
- Social behavior