AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 2 797-R804, Copyright © 1997 by American Physiological Society
Social cues modulate free-running circadian activity rhythms in the diurnal rodent, Octodon degus
N. Goel and T. M. Lee
Department of Psychology, University of Michigan, Ann Arbor 48109-1109, USA.
Two experiments assessed the effects of social cues and daily disturbance
on the circadian locomotor activity rhythms of Octodon degus housed in
constant darkness. In experiment 1, females in free-running conditions were
housed alone or with entrained female partners ("donors") in cages on
either side of a mesh barrier. Donors were removed daily and entrained to 1
h of light, and as a control, the cages of singly housed animals were
rustled daily coincident with donor removal and replacement. None of the
animals housed alone entrained to daily disturbances presented during the
active phase, and seven of eight degus failed to show changes in the
circadian period (tau) or phase of their rhythms. In contrast, although the
presence of entrained donors did not elicit full entrainment of
free-running rhythms, five of six animals demonstrated partial entrainment
for 5-12 days (of 30 days), four of six altered phase of activity onset,
and six of six lengthened tau of circadian rhythms. In experiment 2,
females whose free-running circadian activity rhythms were at least 10 h
out of phase were housed together in pairs. None of the pairs demonstrated
mutual synchronization of their activity rhythms, although 8 of 12 degus
modified phase of activity onset and 9 of 12 animals altered tau. We
conclude social information in the absence of light, is sufficient for
partial entrainment and for changes in tau and phase of free-running
rhythms in this diurnal rodent.
