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.
Subject(s)
Amiodarone/pharmacology , Anti-Arrhythmia Agents/pharmacology , Chemoreceptor Cells/drug effects , Hemodynamics/drug effects , Hypertension, Renal/physiopathology , Animals , Baroreflex/drug effects , Blood Pressure/drug effects , Chronic Disease , Electrophysiology , Heart Rate/drug effects , Male , Rats , Rats, WistarABSTRACT
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 deltapulse 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 percent 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.
Subject(s)
Animals , Male , Rats , Amiodarone/pharmacology , Anti-Arrhythmia Agents/pharmacology , Chemoreceptor Cells , Hemodynamics/drug effects , Hypertension, Renal/physiopathology , Baroreflex/drug effects , Blood Pressure/drug effects , Chronic Disease , Electrophysiology , Heart Rate/drug effects , Rats, WistarABSTRACT
Através de análise ao microscópio de luz, caracterizaram-se quatro tipos de micrópilas em ovócitos vitelogênicos de 19 espécies de teleósteos, baseando-se na ocorrência e profundidade do vestíbulo, no comprimento do canal micropilar e na forma da célula micropilar. Em relaçäo a grupos taxonômicos, quatro espécies de pimelodídeos analisadas mostraram micrópila tipo 1, duas espécies de curimatídeos apresentaram micrópila tipo 2, nos caracídeos foram observados tipos 2, 3 e 4 e, nos anostomídeos, tipos 2 e 4. Os resultados indicam que a morfologia da micrópila e da célula micropilar variam em teleósteos de água doce, podendo apresentar padräo similar em alguns grupos sistemáticos
