Thermal preference behavior in preweaning genetically obese (ob/ob) and lean (+/?, +/+) mice.
Impaired nonshivering thermogenesis and lowered rectal temperatures (Tre) are hallmarks that appear early in the postnatal ontogeny of the genetically obese (ob/ob) mouse. Adult obese mice compensate behaviorally for these impairments and do not defend their low Tres. We predicted that, because young mice primarily rely on behavior to ensure thermal homeostasis during preweaning development, the appearance of the obese mouse's thermoregulatory impairment should promote their continued reliance on behavioral thermoregulation compared to lean pups. Accordingly, intact litters of pups from heterozygous lean (C57BL/6J, ob/+) and from homozygous lean (+/+) matings were tested at 6, 12, and 18 days postpartum on a thermal gradient (14-44 degrees C). Obese pups had lower pretest Tres than lean (+/?) littermates at 6 days and lower pretest Tres than both lean littermates and homozygous (+/+) lean control pups at 12 and 18 days. Exposure to the gradient ameliorated these differences (i.e., no posttest Tre differences among phenotypes). Correspondingly, obese pups preferred warmer gradient locations than +/+ pups but similar locations to their phenotypically lean (+/?) littermates until 18 days, when both lean groups preferred similar thermal locations compared to warmer-seeking obese pups. These data support our hypothesis and emphasize the age-dependent impact of the ob gene on altering mouse pups' thermal preferences.
Wilson
L M
LM
Department of Psychology, University of Manitoba, Winnipeg, Canada.
Currie
P J
PJ
Gilson
T L
TL
D000367:Age Factors; D000818:Animals; D001833:Body Temperature Regulation / Q000235:genetics* / Q000502:physiology; D001835:Body Weight / Q000235:genetics* / Q000502:physiology; D005260:Female; D008297:Male; D051379:Mice; D008820:Mice, Obese; D009043:Motor Activity / Q000235:genetics / Q000502:physiology; D014886:Weaning