C-fos gene expression in rat brain around birth: effect of asphyxia and catecholamines

At birth the mammalian nervous system must adapt rapidly to the neu conditi ons it encounters in the extra-uterine environment. One aspect of this adap tation, known as arousal, is mediated by catecholamines, the Levels of whic h in the brain increase rapidly after birth. The pattern of gene expression also changes. Shortly after birth, expression of the immediate early gene c-fos, known to reflect general neural activity, is up-regulated Furthermor e, asphyxia often occurs in connection with birth. In order to examine the effects of this phenomenon on the expression of c-fos, as well as on the ra te of noradrenaline (NA) turnover, asphyxia was induced in rat pups deliver ed by caesarean section. Northern blot analysis and in situ hybridization r evealed that the increase in expression of c-fos in certain areas of the br ain was greatly enhanced by asphyxia of moderate duration; whereas mere pro longed asphyxia lowered the Level of c-fos mRNA Asphyxia had a similar effe ct on the rate of NA turnover. Adrenergic receptor antagonists administered prior to birth attenuated the birth-related induction of c-fos mRNA. Howev er, the potentiation of c-fos expression by asphyxia was not altered by the se antagonists. Therefore, me propose that while catecholamines play an imp ortant role in the induction of c-fos in the brain at birth, the effects of asphyxia involve a different mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.