Periodic analysis of ultradian (40 min less than tau less than 24h) respiratory variations in laboratory vertebrates of various circadian activities.

: Continuous recordings of respiratory gas exchanges of various laboratory endotherm vertebrate species, which have either a nocturnal (mouse, rat) or diurnal (monkey, quail, chicken) or equivocal (guinea-pig) maximal activity, kept under controlled environmental conditions of temperature, humidity, ventilation and provided with food and water ad libitum, show ultradian oscillations of mean and low frequencies (1 less than f less than 35 c.day-1). Harmonic analysis was used to assess periodic or random ultradian variations and to compute amplitudes and phases of these oscillations when these vertebrates were submitted to a light (100 lx) and dark circadian alteration (LD 12:12). Spectral analysis shows that a 100-lx continuous illumination or continuous darkness decreases circadian respiratory rhythms and increases these ultradian respiratory oscillations.