Manipulation of potential pre- and postnatal zeitgebers for the
juvenile circadian temperature rhythm in rats.
Nuesslein-Hildesheim, B., and I. Schmidt.
Max-Planck-Institut, W. G. Kerckhoff-Institut, Parkstra[beta]e 1,
D-61231 Bad Nauheim, Germany
APStracts 3:0192R, 1996.
We investigated the importance of pre- and postnatal maternal
rhythmicity for the development and synchronization of the juvenile
circadian core temperature (Tc) rhythm in rats by evaluating the Tc
of artificially reared pups in 6 litters derived from mothers
maintained in continuous bright light (LL) and impregnated after
drinking behavior stopped showing circadian periodicity. Pups removed
from their aperiodic mothers on postnatal day 9 and artificially
reared for 3 days showed a free-running Tc rhythm whose amplitude
(3.1+/-0.1 C, N=47) was only slightly smaller than that of control
pups born to mothers maintained in a 12:12 L:D cycle. In 4 litters
the acrophases were synchronized not much less than in the 4 control
litters (mean vector lengths 0.79+/-0.05 vs. 0.94+/-0.04). But only
in 2 litters synchronization among littermates was not significant.
Additional experiments with cross-fostered pups showed that
synchronization is not caused by the time of birth. We conclude that
synchronization among littermates can develop even when maternal
rhythmicity has been suppressed already before conception, possibly
because the Tc decrease of several littermates happening to have
similar phases at birth acts as zeitgeber.
Received 9 February 1996; accepted in final form 1 May 1996.
APS Manuscript Number R84-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96