Daily rhythms of body temperature in Acomys russatus: Their response to photoperiod manipulations and melatonin

1. The effects of photoperiod (16L:8D; 8L:16D) and melatonin treatment (50 mu g for seven days) on daily rhythms of body temperature (T-b) were studied in golden spiny mice Acomys russatus, kept at a constant ambient temperature of 28 degrees C. 2. Results show different patterns of daily T-b rhythms under the different photoperiod regimes. As a response to melatonin, mice under both photoperiods increased T-b while rhythm percentage decreased. A phase shift of about 10 h in T-b acrophase was noted in mice acclimated to 8L:16D. 3. Differences in the patterns of T-b daily rhythms under the different photoperiod regimes, and difference in response to melatonin, may result from higher endogenous melatonin levels in long scotophase acclimated mice. (C) 1997 Elsevier Science Ltd.