title: Ontogeny of an oscillation underlying the circadian rhythm of plasma corticosterone in rats.
abstract: In previous reports (J. Physiol. 325, 493, 507, 521, 1982) we have suggested a prenatal onset of the circadian oscillation in rats. This was based mainly on the findings obtained in pups which were reared by an alternating nursing. In the present study we have applied this technique to experiments which were designed to determine the stage of gestation in the original mother that decided the phase angle of pup's hormone rhythm which was to develop later in the postnatal life. In this experiment we observed, though preliminarily, that reversal of the light-dark cycle of the pregnant mother at day 10 of pregnancy resulted in an effective reversal of pup's hormone rhythm, whereas the reversal at day 17 of pregnancy failed to affect it. From these results it is surmised that the original mother primarily determined the phase angle of the circadian oscillation in the fetus prior to the 17th day of gestation.
mesh_terms: D000375:Aging; D000818:Animals; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood*; D005260:Female; D005333:Fetus / Q000502:physiology; D005865:Gestational Age; D007774:Lactation; D008297:Male; D008431:Maternal-Fetal Exchange; D009991:Oscillometry; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D014886:Weaning
chemical_list: D003345:Corticosterone