Role of Endogenous Angiotensin II on Glutamatergic Actions in the Rostral Ventrolateral Medulla in Goldblatt Hypertensive Rats

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 42; no. 4, Part 2; pp. 707 - 712
• Main Authors: Carvalho, Taís Helena F, Bergamaschi, Cássia T, Lopes, Oswaldo U, Campos, Ruy R
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01.10.2003; Hagerstown, MD Lippincott
• Subjects: Angiotensin II - physiology; Animals; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Blood Pressure - drug effects; Captopril - pharmacology; Cardiology. Vascular system; Excitatory Amino Acid Antagonists - administration & dosage; Excitatory Amino Acid Antagonists - pharmacology; Experimental diseases; Glutamic Acid - administration & dosage; Glutamic Acid - pharmacology; Glycine - administration & dosage; Glycine - pharmacology; Hypertension, Renovascular - physiopathology; Kynurenic Acid - administration & dosage; Kynurenic Acid - pharmacology; Male; Medical sciences; Medulla Oblongata - anatomy & histology; Medulla Oblongata - drug effects; Medulla Oblongata - physiopathology; Microinjections; Rats; Rats, Wistar; Hypertension; Renal artery; Peptides; Rat; Pathogenesis; amino acid; Rodentia; Cardiovascular disease; Glutamate; Sympathetic nervous system; brain; Clip; Vertebrata; Ventrolateral nucleus; Mammalia; Animal; captopril; angiotensin; Angiotensin II
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.HYP.0000086524.35251.2D

ABSTRACT—In this study, we investigated the cardiovascular responses mediated by rostral ventrolateral medulla neurons (RVLM) in the Goldblatt hypertension model (2K-1C) treated or not treated with captopril. The actions of glutamate into the RVLM were tested, injecting glutamate (0.1 mol/L, 100 nL) and its antagonist kynurenic acid (0.02 mol/L, 100 nL). Glycine (0.5 mol/L, 100 nL) was also microinjected. Experiments were performed in male Wistar rats (weight, 250 to 300 g); 5 groups were studied(1) 2K-1C nontreated (H, n=6); (2) 2K-1C treated with captopril, 10 mg/kg per day (Ht10, n=10); (3) 2K-1C treated with captopril, 50 mg/kg per day (Ht50, n=7); (4) control normotensive rats (N, n=7); and (5) normotensive rats treated with captopril, 50 mg/kg per day (Nt50, n=8). All experiments in 2K-1C were performed 6 weeks after renal surgery; captopril treatment lasted for the last 2 weeks. In urethane-anesthetized rats (1.2 g/kg IV), bilateral microinjection of glycine into the RVLM caused a depressor response; there was no difference between groups in relation to the change of variation (N54±2; H46±12; Ht1050±3, and Ht5042±7 mm Hg). Only in the H group, kynurenic acid microinjection into the RVLM caused a depressor response (H158±8 to 132±8 mm Hg). Glutamate response was larger in hypertensive than in normotensive rats (N38±2.6 and H55±6); no difference was observed between hypertensive groups. The data suggest that glutamate acts tonically to drive the RVLM in 2K-1C rats, and this action is modulated by endogenous angiotensin II. The increase in the glutamate actions within the RVLM may contribute to the pathogenesis of renovascular hypertension.