Vol. 94, Issue 2, 677-684, February 2003
Differential metabolic capacity of mice selected for
magnitude of swim stress-induced analgesia
Iwona B.
apo1,
Marek
Konarzewski2, and
Bogdan
Sadowski1,3
1 Institute for Genetics and Animal Breeding, Polish
Academy of Sciences, 05-552 Wólka Kosowska;
2 Institute of Biology, University of Bia
ystok,
15-950 Biaystok; and 3 Department of Experimental
Pathology, Medical Academy of Warsaw, 00-325 Warsaw,
Poland
Maximum oxygen consumption
(
O2) elicited by swimming in 20°C
water or by exposure to 
2.5°C in helium-oxygen (Helox) atmosphere is higher in mice selected for low (LA) than for high (HA)
stress-induced analgesia (SIA) produced by swimming. However,
this line difference is greater with respect to swim- than to
cold-elicited O2. To study the
relationship between the analgesic and thermogenic mechanisms, we
acclimated HA and LA mice to 5°C or to daily swimming at 20 or
32°C. Next, the acclimated mice were exposed to a Helox test at
2.5°C and to a swim test at 20°C to compare
O2 and hypothermia (
T). Cold
acclimation raised O2 and decreased
T. These effects were similar in both lines in the Helox test but
were smaller in the HA than in the LA line in the swim test. HA and LA
mice acclimated to 20 or 32°C swims increased
O2 and decreased T elicited by
swimming, but only HA mice acclimated to 20°C swims increased
O2 and decreased T in the Helox
test. We conclude that the between-line difference in swim
O2 results from a stronger modulation of thermogenic capacities of HA mice by a swim
stress-related mechanism, resulting in SIA. We suggest that the
predisposition to SIA observed in laboratory as well as wild animals
may significantly affect both the results of laboratory measurements of
O2 and the interpretation of its
intra- and interspecific variation.
maximum oxygen consumption; thermogenic capacity; swim stress
