AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 5 1027-R1039, Copyright © 1989 by American Physiological Society
SCN lesions abolish ultradian and circadian components of activity rhythms in LEW/Ztm rats
F. Wollnik and F. W. Turek
Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208.
A trimodal locomotor activity pattern has been observed in LEW/Ztm rats.
Complete and partial lesions of the suprachiasmatic nucleus (SCN) were used
to determine whether the same neural substrate may underlie the circadian
rhythms and the ultradian modulation of wheel-running activity in these
rats. Whereas sham lesions had little or no effect on the wheel-running
activity pattern, complete SCN lesions resulted in a complete loss of
circadian and ultradian activity components under free-running or 12:12 h
light-dark cycle (12:12 LD) conditions. Ultradian and circadian activity
components were still present after partial SCN lesions. Periodogram
analysis for any given animal revealed that the ultradian periods were
always submultiples of the entrained or free-running circadian period.
Furthermore there was a high correlation between the amplitudes of
circadian and ultradian spectral estimates, but with a different slope in
males and females. These results indicate that in LEW/Ztm rats the SCN
contributes to the control of both the circadian wheel-running rhythm and
the trimodal ultradian modulation of that behavior.
