Endocrine Abstracts

Hypothalamo-pituitary-adrenal (HPA) axis responses to stress are attenuated perinatally in mother rodents. We have now investigated the peripheral sympathetic and adrenal medulla responses to stress in pregnancy by measuring noradrenaline and adrenaline secretion after stress. Virgin and pregnant rats were blood sampled before and after exposure to airpuff startle stress in their home cages, and samples analysed for adrenaline, noradrenaline and ACTH concentration by RIA. Airpuff startle increased adrenaline secretion at 2.5 min but not at 10 or 20 min in virgin rats compared to before airpuff and compared to rats not stressed. Adrenaline secretion did not significantly increase in stressed pregnant rats and was significantly less than in virgin rats at 2.5min. These findings mimic those observed for ACTH secretory responses to airpuff startle in pregnant rats. Noradrenaline secretion after airpuff startle increased similarly in both virgin and pregnant rats at 2.5 min after airpuff startle compared to before stress and to unstressed rats. Thus, both HPA axis and adrenaline secretory responses to stress are reduced in late pregnancy. Thus, unlike HPA axis and adrenal medulla responses, peripheral sympathetic responses to stress may be retained in late pregnancy to maintain the mother's ability to respond to threat.

Support: Wellcome Trust.