Antihypertensive Action of Amiodarone in Spontaneously Hypertensive Rats (original) (raw)
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American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2002
It is unknown whether amiodarone exerts a direct central action on the cardiovascular autonomic nervous system. This study was designed to evaluate the effects of acute amiodarone administration on vagal and sympathetic efferent nerve discharges. Experiments were carried out in 25 decerebrate unanesthetized rats. In one group, vagal activity was recorded from preganglionic fibers isolated from the cervical vagus nerve. In another group, sympathetic recordings were obtained from fibers isolated from the cervical sympathetic trunk in intact conditions or after barodenervation. Recordings were performed before and for 60 min after amiodarone (50 mg/kg iv) administration. In all groups, amiodarone induced bradycardia and hypotension. Vagal activity increased immediately, reaching a significant difference after 20 min (260 ± 131% from 16.4 ± 3.3 spikes/s) and was unmodified by the barodenervation. At difference, sympathetic activity after an initial and short-lasting increase (150 ± 83% ...
Comparative effects of amiodarone and dronedarone treatments on cardiac function in a rabbit model
Veterinary World, 2019
Aim: The objective of the study was to compare the effects of amiodarone (AM) and dronedarone (DR) on heart rate variability (HRV) and cardiac contractility in a rabbit model. Materials and Methods: A total of 16 male New Zealand white rabbits were divided into two groups, treated either with AM or DR at incremental dosages of 50 mg/kg/day (AM50 and DR50) and 100 mg/kg/day (AM100 and DR100), orally administrated for 7 days. At the end of each period, electrocardiograms were recorded during consciousness and analyzed using the short-term time and frequency domains of HRV. Standard echocardiography and speckle-tracking echocardiography were studied during immobilization with xylazine and ketamine. Results: The results showed that AM100 and DR100 significantly decreased heart rate, total power, low-frequency component, and low-to-high frequency ratio compared with baselines. Most echocardiogram parameters revealed no significant difference from baselines, except for the global circumferential plane strain rate and time to peak standard deviation of strain, which had statistical significances after treating with AM. Conclusion: Both AM and DR possess negative chronotropy and reduce HRV, which may be explained by their sympathetic suppression and calcium channel blocking activities. Theoretically, both antiarrhythmic drugs may also possess negative inotropy, but only AM is shown to have a negative inotropic effect and reduces cardiac dyssynchrony in this model.