The effect of insulin on the heart rate and temperature of the ground squirrel Spermofilus undulatus during arousal from hibernation

Resumo

The effect of insulin on the heart rate and body temperature, measured per rectum, of ground squirrels (Spermophilus undulatus) during triggered arousal from winter hibernation was studied. We found that the outcomes of insulin injection to hibernating ground squirrels varied in the course of arousal. During the first stage, while body temperatures were less than 10°C, the heart rates and rectal temperatures in both control and insulin-treated groups changed in the same manner. During the next stage of arousal, when the body temperature rose above 12°C, elevation of the heart rate and rectal temperature in the insulin-treated animals was significantly retarded and lasted 110 min compared to 80 min in the control group. Conversely, in the final stage of arousal at body temperatures above 20°C, the heart rate and body temperature increased more rapidly in the insulin-treated animals that reached normal body temperature within 40 min compared to 60 min in the control group. Suggested mechanisms of bidirectional effects of insulin on the heart rates and body temperatures in ground squirrels at the particular stages of arousal, with regard to the progression of endogenous insulin and glucose levels in the blood serum, are discussed.