Ultraviolet-light-evoked phase shifts in the locomotor activity rhythm of the field mouse Mus booduga

The circadian rhythm of locomotor activity in the nocturnal field mouse Mus booduga has been monitored after an exposure to ultraviolet-A (UV-h; wavel ength between 350 and 400 nm) radiation at various hours of the subject's c ycle. The magnitude of the phase shift is used to determine the sensitivity of the circadian pacemaker underlying locomotor activity rhythm. It is obs erved that UV-A shifts the phase of the locomotor activity rhythm in a phas e-dependent manner. ii phase response curve (PRC) is constructed to depict the time course and waveform of the basic oscillator's sensitivity to UV-A radiation. The W-A PRC qualitatively resembles the PRC constructed using di ffused daylight as stimulus. Furthermore, the phase response characteristic s of the circadian pacemaker for UV A suggest a periodically varying sensit ivity to UV-A similar to that to daylight. (C) 1998 Elsevier Science S.A. A ll rights reserved.