Metabolic correlates of selection for swim stress-induced analgesia in laboratory mice.
The upper limits of metabolic rates and the links between maximal and resting metabolic rates in vertebrates have recently received a lot of attention, mainly due to their possible relationship to the evolution of endothermy. We measured peak metabolic rates during 3 min swimming in 20 degrees C water (Vo2swim), maximal metabolic rate (Vo2max) in -2.5 degrees C Helox, and basal metabolic rate (BMR) in two lines of mice selected for high (HA) and low (LA) swim stress-induced analgesia (SSIA). We found that exercise combined with heat loss used for producing SSIA also acted as a selection agent, resulting in a 15% HA/LA line difference in Vo2swim. Core body temperature of HA mice (characterized by lower Vo2swim) was also on average 3.2 degrees C lower than that of LA mice. Furthermore, Vo2max of HA mice was lower than that of LA mice by 8% and accompanied by larger hypothermia. Thus mice with exceptionally high (or low) Vo2max tended to have exceptionally high (or low) Vo2swim, resulting in a positive correlation between Vo2swim and Vo2max. All these suggest that selection for SSIA produced genetically correlated responses in both Vo2swim and Vo2max. However, we did not observe HA/LA differences in BMR. Hence, changes in resting and maximum metabolic rates are not necessarily correlated. We hypothesize that the lack of such a correlation was partially due to the modulation of metabolic responses by SSIA.
Konarzewski
M
M
Institute of Biology, University of Warsaw, Branch in Białystok, Poland.
Sadowski
B
B
Jóźwik
I
I
D000698:Analgesia; D000704:Analysis of Variance; D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D001831:Body Temperature; D005260:Female; D008297:Male; D051379:Mice; D010101:Oxygen Consumption; D010146:Pain / Q000503:physiopathology*; D012044:Regression Analysis; D013312:Stress, Physiological / Q000503:physiopathology*; D013550:Swimming