Cardiovascular regulation and expressions of NO synthase-tyrosine hydroxylase in nucleus tractus solitarius of ovine fetus.
The purpose of this study was to examine cardiovascular responses to fourth cerebral ventricle (4V) administration of nitroglycerin (NTG) or an inhibitor of nitric oxide (NO) synthase (NOS) in the near-term ovine and to determine whether, during birth, neuronal NOS (nNOS) is induced in noradrenergic A1 neurons in the medial nucleus tractus solitarius (mNTS). In chronically instrumented fetal sheep, 4V injection of NTG (1.2 nmol), an NO donor, produced an arterial blood depressor and a moderate decrease in heart rate. Arterial blood pressure is increased by 4V administration of NG-nitro-L-arginine methyl ester (10 nmnol), an inhibitor of NOS, in fetuses. Sections of the medulla from fetuses and newborn lambs were examined by using immunolabeling with tyrosine hydroxylase (TH) antibody combined with NADPH diaphorase (NADPHd) histochemistry, a marker of nNOS activity. The NADPHd-positive cells and TH-positive cells containing NADPHd reactivity were significantly increased in the mNTS of newborns compared with the fetuses. The results suggest that during birth, there is upregulation of NADPHd/nNOS in the noradrenergic neurons of mNTS resulting in a centrally mediated reduction of fetal arterial blood pressure.
Ma
Sheng-Xing
SX
Department of Obstetrics and Gynecology, Harbor-University of California Los Angles Medical Center, UCLA Medical School, Torrance, 90502, USA. ma@humc.edu
Fang
Qun
Q
Morgan
Brian
B
Ross
Michael G
MG
Chao
Conrad R
CR
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D001794:Blood Pressure; D002319:Cardiovascular System / Q000187:drug effects / Q000196:embryology*; D036861:Delivery, Obstetric; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D005260:Female; D005333:Fetus / Q000502:physiology; D009252:NADPH Dehydrogenase / Q000032:analysis; D009474:Neurons / Q000737:chemistry / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D005996:Nitroglycerin / Q000008:administration & dosage; D009638:Norepinephrine / Q000032:analysis; D011247:Pregnancy; D012756:Sheep; D017552:Solitary Nucleus / Q000187:drug effects / Q000196:embryology* / Q000201:enzymology; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis / Q000378:metabolism*
D004791:Enzyme Inhibitors; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D014446:Tyrosine 3-Monooxygenase; D009252:NADPH Dehydrogenase; D005996:Nitroglycerin; D009638:Norepinephrine