Non-shivering thermogenesis in winter-acclimatized and in long-scotophase and cold-acclimated Apodemus mystacinus (Rodentia)

1. 1.|Resistance to cold through non-shivering thermogenesis (the absolute increase in O₂ consumption caused by noradrenaline injection) was increased 3-fold in individuals of the broad-toothed mouse A. mystacinus, kept for 3 weeks under a short photoperiod (long scotophase 8L:16D) at an ambient temperature of 28°C, compared to control conditions (12L:12D; 28°C), and did not differ significantly from the winter-acclimatized group.

2. 2.|Acclimation of the same individuals to long scotophase and cold (8L:16d; 7°C) caused a significant (P < 0.01) increase in absolute O₂ consumption and maximal body temperature, as a response to noradrenaline injectin, when compared to long-scotophase individuals (8L:16D; 28°C).

3. 3.|The results of this study support the idea that winter acclimatization of heat-production mechanisims may be induced by the extension of scotophase, which cycles very regulary in nature and in the Mediterranean region occurs before the beginning of the cold season.

Author Keywords: Non-shivering thermogenesis; long scotophase; winter acclimatization; photoperiod; resistance to cold; Apodemus mystacinus