OWEN-ASHLEY, N. T.*; TURNER, M.; HAHN, T. P.; WINGFIELD, J. C.; Univ. of Washington, Seattle; Univ. of Washington, Seattle; Univ. of California, Davis; Univ. of Washington, Seattle: Hormonal, behavioral, and thermoregulatory consequences of lipopolysaccharide-induced sickness in the White-crowned Sparrow (Zonotrichia leucophrys gambelii)
Exposure to pathogens or inflammatory stimuli such as bacterial lipopolysaccharide (LPS) activates the vertebrate immune system and initiates a cascade of behavioral, hormonal, and metabolic changes that are collectively termed the acute phase response. This response includes fever, anorexia, and stereotypical sickness behaviors, such as lethargy and a reduction in food and water intake, along with alterations in glucocorticoid and sex steroid levels. The acute phase response is well-described in mammals, but unexplored in passerine birds. Captive male and female white-crowned sparrows (Zonotrichia leucophrys gambelii) were housed on short (8L:16D) or long (20L:4D) day lengths and injected i. p. with either LPS or saline (control). LPS activated the hypothalamo-pituitary-adrenal axis, causing a rapid increase in plasma corticosterone levels over 24 hrs compared to controls. Suppression of the reproductive axis also occurred in long day LPS birds as measured by a decline in luteinizing hormone levels. Instead of a rise in body temperature, LPS birds experienced short-term hypothermia compared to controls. LPS caused a marked decline in activity and a reduction in food and water intake, resulting in anorexia. LPS males on long days experienced more severe anorexia than LPS males on short days, but this effect was not observed in females. This result paralleled differences in body condition. Long day males were heavier and had larger fat depots than short day males while short and long day females did not differ in mass or fat reserves. Given that the expression of sickness is costly, these results suggest that modulation of the acute phase response is closely linked to physiological condition and energy reserves.
