AJP - Regulatory, Integrative and Comparative Physiology, Vol 246, Issue 3 359-R363, Copyright © 1984 by American Physiological Society
Further evidence that circadian rhythm of blinded rat pups is entrained by the nursing dam
K. Takahashi, N. Murakami, C. Hayafuji and Y. Sasaki
To determine the importance of the nursing mother in setting the phase of
the endogenous rhythm in blinded rat pups, free-running rhythm of locomotor
activity in the pups was observed during 4-5 wk after weaning. Blinded
pups, optically enucleated on day 1, were raised by either an intact
natural mother or an intact foster mother with a rhythm reversed to that of
the natural mother. The locomotor activity was continuously recorded for
4-5 wk, starting between 3 and 5 postnatal wk. At 5 wk of age the offset
time of activity phase was found during the periods corresponding to the
middle half of the light phase in the nursing period, regardless of whether
they were raised by a natural or a foster mother. The free-running periods,
in the blinded pups tested, were fairly close, with the majority ranging
between 24.3 and 24.5 h. These findings indicate that the endogenous rhythm
of the blinded pups is entrained by the nursing mother during the nursing
period.
