THE CIRCADIAN-RHYTHM OF THERMOREGULATION IN JAPANESE-QUAIL .2. MULTIOSCILLATOR CONTROL

Most biochemical, physiological, and behavioral processes in vertebrat es show significant daily rhythms. Under constant conditions, these rh ythms exhibit an endogenous periodicity around 24 h showing that they are driven by an internal circadian clock. In Japanese quail, the circ adian clock driving activity and body temperature rhythms is functiona lly organized as a dual-oscillator system. Under certain conditions, s uch as switching birds from light:dark (LD) 12:12 to continuous darkne ss (DD), the body temperature rhythm splits into two circadian compone nts that free-run independently before recoupling in a normal phase-re lationship. The behavior of the activity rhythm parallels that of the body temperature rhythm, supporting the hypothesis that both rhythms a re driven by the same set of oscillators. In some instances, recouplin g fails to occur and birds continue to exhibit two circadian component s that free-run independently. Dual-oscillator control of body tempera ture was observed in normal birds, pinealectomized birds, and optic ne rve sectioned birds. However, birds were rendered arrhythmic by comple te eye removal. It is proposed that the central circadian system (supr achiasmatic nuclei?) acts as a complex pacemaker that is functionally organized as two sets of oscillators and that circadian input from the eyes is necessary to preserve the integrity of this complex pacemaker .