Abstract
A group of pregnant control rats was sacrificed before parturition, in the morning,
afternoon and evening of day 20 and 21 and in the morning of day 22. Another group
was sacrificed during parturition, when 2 to 8 foetuses had been expelled. The onset
of parturition occurred for the first rat in the afternoon of day 21 and for the last
rat in the afternoon of day 22. Corticosterone was extracted from maternal, foetal
and neonatal adrenals and plasma, and was assayed by a fluorometric procedure.
The maternal adrenal and plasma corticosterone levels, before parturition, were lower
in the morning than in the afternoon excepting day 22 when morning values were as
high as those in the afternoon of day 21.
Adrenal and plasma corticosterone concentrations were elevated during parturition
in the mother but not the foetus. Plasma corticosterone values were raised in the
newborn compared to their littermates in utero.
Key words
Parturition - Adrenal and Plasma Corticosterone - Pregnant Rat - Foetus - Newborn
