MODULATION OF THE CIRCADIAN RHYTHM OF BODY TEMPERATURE BY INTENSE ACTIVITY IN A SUBTERRANEAN RODENT (Ctenomys cf. knighti)

TACHINARDI P; - TOMOTANI BM; FLÔRES DEFL; BICUDO JEW; VALENTINUZZI VS; ODA GA

Puebla

Congreso; Third World Congress on Chronobiology; 2011

Most mammals show a daily body temperature (Tb) rhythm which is endogenous and entrained by light/dark (LD) cycles. Usually, the highest temperatures occur during the same phase of motor activity, which often may mislead to the conclusion that the Tb rhythm is a mere consequence of the activity/rest rhythm. Nevertheless, several studies have verified that both rhythms persist independently of each other. Intense activity may, however, modulate some parameters of the Tb rhythm. Quantifying this modulation helps dissecting the exogenous and endogenous components of the Tb rhythm when the animal is under different experimental conditions or in its natural habitat. We investigated this issue in a subterranean rodent, the tuco-tuco (Ctenomys cf. knighti), found in northwest Argentina. First we studied their Tb under an LD cycle and verified a daily Tb rhythm with the highest temperatures occurring during the dark, synchronously to running-wheel activity. Furthermore, Tb rhythm persisted under constant darkness (DD), an evidence of its endogenous nature. Interestingly, we observed a much smaller variability in rhythmic patterns (period, phase and amplitude) compared to other subterranean rodents. In order to study the exogenous components of the Tb rhythm due to intense activity, its parameters in the presence and absence of a running-wheel were compared. To continuously measure temperature and gross motor activity, telemetric transmitters were implanted intraperitoneally. Three tuco-tucos were kept individually in cages equipped with running-wheels and exposed to the following lighting conditions: 1) DD (44 days); 2) LD (12:12, 14 days); 3) reestablishment of DD (16 days). The wheels were then removed and the exposure to the lighting conditions repeated. After running-wheel removal, mean gross motor activity diminished 54-62% in two animals. Free-running period (ranging from 23.6 to 24.4 hours) and phase relationship with activity rhythm did not change significantly. The amplitude, in turn, decreased about 0.5oC in 2 animals. These results will be important for further analysis of experiments using running-wheels as well as studies of Tb rhythmicity of tuco-tuco?s in their natural habitat, where they show frequent bouts of intense activity while digging.