COMPARISON OF ULTRADIAN AND CIRCADIAN OSCILLATIONS OF CARBON-DIOXIDE PRODUCTION BY VARIOUS ENDOTHERMS

Carbon dioxide emission (VCO2) was computed every 20 min from continuous CO2 concentration recordings taken during 3-30 consecutive days, in strictly controlled environmental conditions, in 54 OF1 mice, 99 Japanese quail, 66 Sprague-Dawley rats, 50 Hartley guinea pigs, 7 chicks, for 1-15 days on 2 Cynomolgus monkeys, and for 24 h on 7 premature infants. This VCO2 shows circadian and ultradian oscillations that were analyzed for frequencies and amplitudes in Light-dark 12-h alternation (LD 12:12), continuous light (LL), and continuous dark (DD). Circadians were not always identified or were often masked in LL or DD (mostly in guinea pigs, quail, and rats), while ultradians (tau greater than or equal to 40 min) were found in all species, at every time, and in all light regimens. Analysis of variance and chi(2) show significant (P < 0.001) interspecies differences for ultradian (1.07 < tau < 1.40 h) intervals and for circadian and ultradian VCO2 amplitudes. Relationships between ultradian and circadian VCO2 oscillations differ according to the species, ultradians appearing as an entity characteristic for each endotherm species.