Effect of selection for behavior on the blood glucose level in foxes exposed to restriction stress

Selection of silver foxes for attitude to humans influences the hypothalamus-pituitary-adrenal axis and sympathetic nervous system, which, in turn, are involved in the regulation of carbohydrate metabolism under stress. It has also been shown that heredity affectes carbohydrate metabolism and glucose tolerance. It remains to find out whether the selection for attitude to humans affected carbohydrate metabolism and blood glucose levels in silver foxes. We studied basal blood glucose levels in tame, aggressive, and unselected male and female silver foxes and glucose levels in females exposed to stress. Our results indicate that the basal blood glucose level in tame foxes is significantly lower than in unselected or aggressive ones regardless of sex. In unselected males, this parameter was lower than in aggressive animals. Aggressive foxes showed a sex difference in the basal blood glucose level: it was higher in males than in females. The glucose levels in aggressive females remained higher than in tame ones immediately after 10-min stress and two hours afterwards. Only aggressive females showed an excess blood glucose level over the basal one two hours after stress. The bulk group of foxes demonstrated a negative correlation between blood glucose and behavior score (response to humans) both at rest and after stress. A glucose tolerance test (GTT) was performed to compare the rates of glucose absorption from the bloodstream in silver fox females selected for behavior. Although selection for behavior did not affect glucose tolerance, judging from the area under the GTT curves, aggressive females differed from tame and unselected at the beginning of the test in longer persistence of elevated blood glucose. Thus, the selection of silver foxes for attitude to humans influences blood glucose levels at rest in both sexes and after stress in females.