Chronic effects of interleukin-1 beta on fever, oxygen consumption and food intake in the rat.
Chronic subcutaneous infusion (from osmotic minipumps) of IL-1 beta (1 microgram/d) in male rats over seven days caused transient (1-3 d) increases in body temperature and reductions in body weight gain and food intake. By day 3, when colonic temperature was similar for vehicle and IL-1 infused groups, the acute responses (increases in temperature and VO2) to a maximal dose (1 microgram, sc) of IL-1 beta was almost identical in all animals. In a separate study intraperitoneal infusion of the same dose of IL-1 beta (1 microgram/d) increased the duration of changes in body temperature, weight and food intake, compared to subcutaneous infusion. In further groups of rats, pyrogenic responses to daily injections of IL-1 beta (1 microgram ip) were sustained for the entire 7 d period, but this treatment did not affect body weight. These data demonstrate that tolerance to infusion of IL-1 is not accompanied by reduced maximal responses to acute administration of IL-1, and indicate that more sustained effects of IL-1 are achieved by intraperitoneal rather than subcutaneous infusions, or by repetitive daily injections of the cytokine. These observations indicate that low levels of IL-1 release, maintained over periods of several days could be responsible for changes in body temperature and energy balance during chronic infections or inflammation.
Dept. of Physiological Sciences, University of Manchester, United Kingdom.
N J
NJ
Busbridge
M J
MJ
Dascombe
N J
NJ
Rothwell
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D004343:Drug Implants; D004435:Eating / Q000187:drug effects*; D007274:Injections, Intraperitoneal; D007375:Interleukin-1 / Q000494:pharmacology*; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004343:Drug Implants; D007375:Interleukin-1