title: Acute effect of amiodarone on cardiovascular reflexes of normotensive and renal hypertensive rats.
abstract: The aim of the present study was to evaluate the effect of amiodarone on mean arterial pressure (MAP), heart rate (HR), baroreflex, Bezold-Jarisch, and peripheral chemoreflex in normotensive and chronic one-kidney, one-clip (1K1C) hypertensive rats (N = 9 to 11 rats in each group). Amiodarone (50 mg/kg, iv) elicited hypotension and bradycardia in normotensive (-10 +/- 1 mmHg, -57 +/- 6 bpm) and hypertensive rats (-37 +/- 7 mmHg, -39 +/- 19 bpm). The baroreflex index (deltaHR/deltaMAP) was significantly attenuated by amiodarone in both normotensive (-0.61 +/- 0.12 vs -1.47 +/- 0.14 bpm/mmHg for reflex bradycardia and -1.15 +/- 0.19 vs -2.63 +/- 0.26 bpm/mmHg for reflex tachycardia) and hypertensive rats (-0.26 +/- 0.05 vs -0.72 +/- 0.16 bpm/mmHg for reflex bradycardia and -0.92 +/- 0.19 vs -1.51 +/- 0.19 bpm/mmHg for reflex tachycardia). The slope of linear regression from delta pulse interval/deltaMAP was attenuated for both reflex bradycardia and tachycardia in normotensive rats (-0.47 +/- 0.13 vs -0.94 +/- 0.19 ms/mmHg and -0.80 +/- 0.13 vs -1.11 +/- 0.13 ms/mmHg), but only for reflex bradycardia in hypertensive rats (-0.15 +/- 0.02 vs -0.23 +/- 0.3 ms/mmHg). In addition, the MAP and HR responses to the Bezold-Jarisch reflex were 20-30% smaller in amiodarone-treated normotensive or hypertensive rats. The bradycardic response to peripheral chemoreflex activation with intravenous potassium cyanide was also attenuated by amiodarone in both normotensive (-30 +/- 6 vs -49 +/- 8 bpm) and hypertensive rats (-34 +/- 13 vs -42 +/- 10 bpm). On the basis of the well-known electrophysiological effects of amiodarone, the sinus node might be the responsible for the attenuation of the cardiovascular reflexes found in the present study.
authors.affiliation: Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, 14049-900 Ribeirão Preto, SP, Brasil.
authors.forename: P F
authors.initials: PF
authors.lastname: Oliveira
authors.forename: V J
authors.initials: VJ
authors.lastname: Dias da Silva
authors.forename: M C O
authors.initials: MC
authors.lastname: Salgado
authors.forename: R
authors.initials: R
authors.lastname: Fazan
authors.forename: C A
authors.initials: CA
authors.lastname: Aguiar
authors.forename: H C
authors.initials: HC
authors.lastname: Salgado
mesh_terms: D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D017704:Baroreflex / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002628:Chemoreceptor Cells / Q000187:drug effects*; D002908:Chronic Disease; D004594:Electrophysiology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006977:Hypertension, Renal / Q000503:physiopathology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000889:Anti-Arrhythmia Agents; D000638:Amiodarone