Captopril blocks the cardiac actions of centrally administered angiotensin I in the trout Oncorhynchus mykiss

• Published in: Brain research 2004-05, Vol.1007 (1), p.116-123
• Main Authors: Lancien, Frédéric, Mimassi, Nagi, Mabin, Dominique, Le Mével, Jean-Claude
• Format: Article
• Language: English
• Subjects: Angiotensin I; Angiotensin I - administration & dosage; Angiotensin I - pharmacology; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors - pharmacology; Animals; Biological and medical sciences; Captopril; Captopril - pharmacology; Drug Interactions; Electroencephalography; Endopeptidases - pharmacology; Fourier Analysis; Fundamental and applied biological sciences. Psychology; Heart - drug effects; Heart rate; Heart Rate - drug effects; Heart rate variability; Injections, Intraventricular; Oncorhynchus mykiss; Renin–angiotensin system; Short-time Fourier transform; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Statistics, Nonparametric; Time Factors; Trout; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2004.02.012

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 μg) 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.