AJP - Regulatory, Integrative and Comparative Physiology, Vol 272, Issue 1 172-R182, Copyright © 1997 by American Physiological Society
Eye and gonad: role in the dual-oscillator circadian system of female Japanese quail
H. Underwood, T. Siopes and K. Edmonds
Department of Zoology, North Carolina State University, Raleigh 27695-7617, USA. Herbert_Underwood@ncsu.edu
Experiments were conducted to determine the anatomic and physiological
basis of the dual-oscillator circadian system of female Japanese quail.
After blocking of ocular light perception by eye-patching, the circadian
body temperature rhythm dissociates into two circadian components in
continuous lighting (LL). One component free runs with a period
significantly shorter than 24 h [mean period (tau) = 22.7 h] and is driven
by an ocular pacemaker, whereas the other component free runs with a period
significantly longer than 24 h (tau = 26.3 h). The long free-running rhythm
is driven by the same circadian clock that drives the circadian rhythm of
ovulation. The expression of the long free-running rhythm in LL depends on
the presence of the ovary: body temperature rhythmicity is abolished by
ovariectomy. The two free-running oscillators in eye-patched birds showed
evidence of mutual interaction. Significantly, the phase relationships that
occur as the two oscillators interact can determine whether or not
ovulation occurs. The results are discussed in terms of an "internal
coincidence" mechanism for photoperiodic time measurement.
