Effect of different doses of noradrenaline against ischemia-induced ventricular arrhythmias in rat heart in vivo.
BACKGROUND
The present study was designed to evaluate the preconditioning effect of different doses of noradrenaline on ischemia-induced ventricular arrhythmias in open chest anesthetized rats.


METHODS
The anaesthetized rats were subjected to 25 min of regional ischemia by left descending coronary artery (LAD) occlusion. In sham group, surgical procedures were done but ischemia was not applied. In control rats, saline was injected prior to ischemia. In noradrenaline groups, rats pretreated with three different doses of noradrenaline (respectively, 0.5, 1 and 2 microg/kg, IV).


RESULTS
In control rats, induction of ischemia shortened the QTc (corrected QT) interval (ms) and led to occurrence of ventricular arrhythmias. Administration of low-dose of noradrenaline prevented shortening of the QTc interval during ischemia but could not significantly attenuate severity and incidences of arrhythmias. Injection of mid-dose of noradrenaline stabilized the QTc during ischemia and reduced severity of arrhythmias. Pretreatment with high-dose of noradrenaline significantly prolonged the QTc interval and declined severity and incidence of arrhythmias.


CONCLUSIONS
Noradrenaline dose-dependently attenuated ischemia-induced ventricular arrhythmias.
Imani
Alireza
A
Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, IR Iran.
Faghihi
Mahdieh
M
Keshavarz
Mansoor
M
Karimian
Seyed Morteza
SM
Niaraki
Somayeh Sadeghi
SS