title: Captopril blocks the cardiac actions of centrally administered angiotensin I in the trout Oncorhynchus mykiss.
abstract: The present study was performed in order to gain new insights into the existence of a brain renin-angiotensin system (RAS) in teleost fish. For this purpose, we investigated the effects of centrally administered angiotensin (ANG) I ([Asn(1),Val(5),Asn(9)]ANG I) and ANG II ([Asn(1),Val(5)]ANG II) on heart rate (HR) and heart rate variability (HRV) in the unanesthetized trout. The animals were studied before and after treatment with captopril, an angiotensin-converting enzyme (ACE) inhibitor. Trout were equipped with two subcutaneous electrocardiographic electrodes and with an intracerebroventricular (i.c.v.) cannula inserted within the third ventricle of the brain. The i.c.v. injection of vehicle had no effect on the recorded parameters. The i.c.v. injections of ANG I and ANG II at doses of 5 and 50 pmol had a marked effect on HR and HRV. At a dose of 50 pmol, ANG I and ANG II produced a progressive and significant increase in HR (+36% and+45%, respectively) but elicited a profound decrease in HRV (-88% and-92%, respectively). I.c.v. injection of captopril (10 microg) had no effect on HR or HRV. However, this ACE inhibitor prevented the tachycardia and abolished the decrease in HRV mediated by 50 pmol of ANG I. In contrast, captopril had no effect upon the cardiac actions of 50 pmol of ANG II. These results give the first support for the existence of functional important ACE-like activity in the brain of a teleost fish and suggest that the brain RAS in this class of vertebrate may be involved in the control of cardiac chronotropic activity.
authors.affiliation: LaTIM (EA 2218), INSERM U 650, Laboratoire de Neurophysiologie, Faculté de Médecine et des Sciences de la Santé, Université de Bretagne Occidentale, 22 avenue Camille Desmoulins, CS 93837, 29238, Brest Cedex 3, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lancien
authors.forename: Nagi
authors.initials: N
authors.lastname: Mimassi
authors.forename: Dominique
authors.initials: D
authors.lastname: Mabin
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Le Mével
mesh_terms: D000803:Angiotensin I / Q000008:administration & dosage / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D002216:Captopril / Q000494:pharmacology*; D004347:Drug Interactions; D004569:Electroencephalography; D010450:Endopeptidases / Q000494:pharmacology; D005583:Fourier Analysis; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D007276:Injections, Intraventricular; D017686:Oncorhynchus mykiss; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000803:Angiotensin I; D002216:Captopril; D010450:Endopeptidases; C047491:angiotensin-producing serum enzyme II