title: Angiotensin-(1-7) antagonist, A-779, microinjection into the caudal ventrolateral medulla of renovascular hypertensive rats restores baroreflex bradycardia.
abstract: In the present study we evaluated the effect of caudal ventrolateral medulla (CVLM) microinjection of the main angiotensin (Ang) peptides, Ang II and Ang-(1-7), and their selective antagonists on baseline arterial pressure (AP) and on baroreceptor-mediated bradycardia in renovascular hypertensive rats (2K1C). Microinjection of Ang II and Ang-(1-7) into the CVLM of 2K1C rats produced similar decrease in AP as observed in Sham rats. In both Sham and 2K1C, the hypotensive effect of Ang II and Ang-(1-7) at the CVLM was blocked, for up to 30 min, by previous CVLM microinjection of the Ang II AT1 receptor antagonist, Losartan, and Ang-(1-7) Mas antagonist, A-779, respectively. As expected, the baroreflex bradycardia was lower in 2K1C in comparison to Sham rats. CVLM microinjection of A-779 improved the sensitivity of baroreflex bradycardia in 2K1C hypertensive rats. In contrast, Losartan had no effect on the baroreflex bradycardia in either 2K1C or Sham rats. These results suggest that Ang-(1-7) at the CVLM may contribute to the low sensitivity of the baroreflex control of heart rate in renovascular hypertensive rats.
authors: Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil.
authors: Luiza Michelle
authors: LM
authors: Cangussu
authors: Uberdan Guilherme Mendes
authors: UG
authors: de Castro
authors: Raquel
authors: R
authors: do Pilar Machado
authors: Marcelo Eustáquio
authors: ME
authors: Silva
authors: Patrícia Maria
authors: PM
authors: Ferreira
authors: Robson Augusto Souza
authors: RA
authors: dos Santos
authors: Maria José
authors: MJ
authors: Campagnole-Santos
authors: Andréia Carvalho
authors: AC
authors: Alzamora
mesh_terms: D000803:Angiotensin I / Q000037:antagonists & inhibitors*; D000804:Angiotensin II / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects*; D001919:Bradycardia; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000503:physiopathology; D019808:Losartan / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000187:drug effects*; D008845:Microinjections; D010446:Peptide Fragments / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: C092006:7-Ala-angiotensin (1-7); D000959:Antihypertensive Agents; D010446:Peptide Fragments; D000804:Angiotensin II; D000803:Angiotensin I; C118790:angiotensin I (1-7); D019808:Losartan