Retention of carbon dioxide during entrance into torpor in dormice

Metabolic rate (MR), heart rate (HR) and body temperature (T-b) of two edib le dormice (Glis glis) were studied during entrance into torpor at two temp erature ranges, T-a=0 to 5 degreesC and 15 to 20 degreesC. MR was reduced r apidly from 275 to 84 ml O-2*h(-1) within the first hour after onset into t orpor at the low temperature range and from 154.5 to 82.2 mi O-2*h(-1) at t he high temperature range. HR decrease paralleled the reduction of MR. Betw een 0-5 degreesC the HR decreased rapidly from 388 to 171 BPM within the fi rst hour and from 284 to 193 BPM in the range of 15-20 degreesC. After the onset of metabolic reduction T-b decreased within one hour from 36.9 degree sC to 30.8 degreesC at the low temperature range (cooling rate 6.1 degreesC *h(-1)). At the high temperature range cooling rate within the first hour w as at 2.4 degreesC*h(-1) with a T-b decrease from 37.2 degreesC to 34.8 deg reesC. A decrease of respiratory quotient (RQ) appeared closely correlated to the reduction of T-b at T-a below 5 degreesC. The RQ decreased to 0.25 i ndicating a retention of CO2. In the temperature range of 15 to 20 degreesC no reduction of RQ could be observed during entry into torpor. The Ra even rose slightly from 0.7 - 0.8 to about 1.0. We suggest that the depression of metabolism and heart activity is an active downregulation, but the decre ase of RQ at low T-b point out a temperature dependent relationship caused by cooling of body fluids.