Effect of NOS inhibition on central response to atrial distension during pregnancy.
Atrial distension increases c-fos expression in the paraventricular nucleus of virgin, but not pregnant, rats. We proposed that nitric oxide (NO), biosynthesis of which increases during pregnancy, blunts this reflex and that blocking NO biosynthesis would restore the response. Female rats were implanted with indwelling intracardiac balloons. On day 14 of pregnancy, osmotic minipumps containing either D- or N(G)-nitro-L-arginine methyl ester (L-NAME) (120 mg/2 ml at 10 microg/min) were implanted. On day 20, the rats were infused with saline (3 ml/h) with or without atrial balloon inflation (1 h). The brains were then processed for quantitation of c-fos expression. In the virgin rats, and in the pregnant rats treated with L-NAME, atrial distension significantly increased hypothalamic c-fos expression. In the pregnant animals treated with D-NAME, the response was greatly attenuated. NO had no effect on the increase in atrial receptor afferent discharge (single-fiber recordings) elicited by atrial distension. We conclude that, during pregnancy, NO attenuates central processing of the reflex response to atrial distension but does not alter the transducer properties of the volume receptors.
Tam
Siu Lin
SL
Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2S2.
Sims
Elaine
E
Kaufman
Susan
S
D000818:Animals; D016275:Atrial Function / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D002404:Catheterization; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D007260:Infusion Pumps; D008465:Mechanoreceptors / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans
D004791:Enzyme Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester