Effect of pregnancy on activation of central pathways following
atrial distention.
Deng, Yiming, and Susan Kaufman.
Department of Medicine, 475 Heritage Medical Research Centre,
University of Alberta, Edmonton, Alberta, Canada, T6G 2S2
APStracts 2:0088R, 1995.
Stimulation of the atrial volume receptors increases neural traffic to
the ventrolateral medulla which in turn sends output to, and receives
input from, the lateral hypothalamic area. An integrated reflex and
hormonal response is thus initiated. We wished to investigate first
whether atrial distention results in activation of selected nuclei in
the forebrain and, secondly, whether pregnancy modifies this
response. Rats were implanted with indwelling intracardiac balloons
positioned at the superior vena caval/ right atrial junction. One
week later, the balloons were inflated. The animals were then
anesthetized, their brains fixed by perfusion, and the tissue
prepared for visualization of c-fos activity. Atrial distention
caused a significant increase in c-fos expression in the
paraventricular nucleus, the medial preoptic area and the lateral
septum. This response was markedly attenuated in the pregnant
animals. In conclusion, during pregnancy central pathways that are
normally activated in responses to volume expansion, fail to respond
to atrial distention. We propose that this allows blood volume to
increase in the pregnant animal, without triggering homeostatic
mechanisms.
Received 21 September 1994; accepted in final form 23 March 1995.
APS Manuscript Number R545-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 April 1995.