ABSTRACT
1. The primary aim of this investigation was to ascertain the effects of thiopentone sodium and diethyl ether as anaesthetics on plasma catecholamine levels of Sprague-Dawley and Long-Evans rats. A secondary aim was to investigate the effect of norepinephrine on susceptibility to electrically induced arrhythmia in the Langendorff perfused isolated rat heart. 2. Thiopentone sodium anaesthesia resulted in significantly lower plasma norepinephrine and epinephrine levels when compared with diethyl ether anaesthesia. 3. Long-Evans rats exhibited significantly higher epinephrine levels regarding both anaesthetics in comparison with their Sprague-Dawley counterparts. 4. If plasma catecholamines are an indicator of the level of induced stress then diethyl ether anaesthesia resulted in more stress both of a psychological and physiological origin when compared with thiopentone sodium anaesthesia. 5. Long-Evans rats seem to be more prone to the physiologically-induced component of stress than Sprague-Dawley rats. 6. In isolated hearts, norepinephrine increased susceptibility (P less than 0.002) to electrically induced arrhythmia. This occurred at a concentration corresponding to measured upper levels of total catecholamines in diethyl ether anaesthetised animals.
