title: Role of endogenous angiotensin II on glutamatergic actions in the rostral ventrolateral medulla in Goldblatt hypertensive rats.
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 (N: 54+/-2; H: 46+/-12; Ht10: 50+/-3, and Ht50: 42+/-7 mm Hg). Only in the H group, kynurenic acid microinjection into the RVLM caused a depressor response (H: 158+/-8 to 132+/-8 mm Hg). Glutamate response was larger in hypertensive than in normotensive rats (N: 38+/-2.6 and H: 55+/-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.
authors.affiliation: Federal University of São Paulo, School of Medicine, São Paulo, Brazil.
authors.forename: Taís Helena F
authors.initials: TH
authors.lastname: Carvalho
authors.forename: Cássia T
authors.initials: CT
authors.lastname: Bergamaschi
authors.forename: Oswaldo U
authors.initials: OU
authors.lastname: Lopes
authors.forename: Ruy R
authors.initials: RR
authors.lastname: Campos
mesh_terms: D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D018698:Glutamic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D005998:Glycine / Q000008:administration & dosage / Q000494:pharmacology; D006978:Hypertension, Renovascular / Q000503:physiopathology*; D007736:Kynurenic Acid / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000187:drug effects / Q000503:physiopathology*; D008845:Microinjections; D051381:Rats; D017208:Rats, Wistar
chemical_list: D018691:Excitatory Amino Acid Antagonists; D000804:Angiotensin II; D018698:Glutamic Acid; D002216:Captopril; D007736:Kynurenic Acid; D005998:Glycine