The manifestation of circadian rhythm under constant light depends
on the lighting conditions during lactation.
Cambras, T., M. M. Canal, A. Torres, J. Vilaplana, A. D[acute]iez
-Noguera.
Unitat Fisiologia. Facultat Farmacia. Universitat de Barcelona,
08028 Barcelona
APStracts 3:0389R, 1996.
Adult rats transferred to continuous illumination (LL) show a
disruption of circadian rhythms, although the mechanisms underlying
this effect are not yet well known. In previous experiments we found
that when rats were born and raised under LL they showed an ultradian
pattern during the first 10 days after weaning, but afterwards they
generated a circadian rhythm that was maintained until adulthood. It
was not clear whether this evolution was due to the influence of the
rhythm of the mother or to the effect of constant light. Here, we
have studied the motor activity rhythm of young rats maintained under
LL after weaning, taking into account the conditions to which they
were exposed during lactation (LL or DD). To check the possible
effect of the rhythm of the dam, on the day of delivery some of the
dams were blinded, others were subjected to a restricted feeding
schedule of 3 hours per day and the others were used as control. For
each rat, the period of the circadian rhythm and the percentage of
variance explained by this rhythm were calculated. Results show that
all the rats maintained under LL during lactation expressed a
circadian rhythm in their motor activity. However, rats maintained
under DD during lactation did not. This effect did not seem to be
dependent on the type of dam. These results suggest that the rhythm
of the dams does not affect the manifestation of the rhythm of the
pups, and that the expression of circadian rhythmicity under constant
bright light depends on the lighting conditions under which the
animals were maintained during lactation, which could affect the
development of the circadian pacemaker or the retina.
Received 3 May 1996; accepted in final form 23 September 1996.
APS Manuscript Number R250-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996