Behavioral and Physiological Responses to Lipopolysaccharide in the Chicken
Recent evidence indicates that many of the physiologic, metabolic, and behavioral responses that accompany infection in mammals are important for maintaining homeostasis and promoting recovery. We have extended this concept to birds by demonstrating that lipopolysaccharide (LPS) injected intraperitoneally (i.p.) increases body temperature (T$\sb{\rm b}$), reduces feed intake, increases somnolence, decreases plasma (Fe) and (Zn), increases plasma (Cu), and elevates plasma corticosterone. To determine if any of these responses could be mediated centrally, LPS was injected intracerebroventricularly (i.c.v.). Whereas i.p. injection of LPS caused a modest increase in T$\sb{\rm b}$, the hyperthermic response to LPS injected i.c.v. was intense and long-lasting. This hyperthermia following i.c.v. injection of LPS was accompanied by only a transient reduction in food intake and elevation in sleep activity, with no change in plasma (Fe) or (Zn). Both peripheral and central injections of LPS increased plasma corticosterone, but the increase caused by i.p. administered LPS was 6-fold higher than that caused by LPS injected i.c.v. Collectively, these data show that chickens respond behaviorally and physiologically to both peripheral and central injections of endotoxin. However, the magnitude of these responses depends upon whether LPS acts at central or peripheral sites. To investigate the role of prostaglandins (PGs) in the behavioral and physiological responses to LPS, chickens were injected with indomethacin i.p. or i.c.v. and their behavior and T$\sb{\rm b}$ following a challenge i.p. injection of LPS was measured. Our results are interpreted to indicate that LPS induces hyperthermia in the chicken by activating a PG system in the brain. Peripheral but not central PGs appear to induce an anorexic response to LPS, whereas both peripheral and central PGs may be involved in the somnolent effects of LPS. The involvement of multiple PG systems during the acute-phase response may provide an opportunity for pharmacological intervention of sickness.
Biology, Animal Physiology, Agriculture, Animal Pathology, Biology, Veterinary Science
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign