Effect of acute stress and ouabain administration on adrenal catecholamine content and cardiac function of rats pretreated with diazepam.

The experiments described were carried out in an attempt to determine the participation of adrenal catecholamines in the higher incidence of cardiac arrhythmias produced by acute stress or ouabain injections in diazepam-treated animals. The pretreatments of rats with diazepam (150 mg kg-1 d-1) increase significantly the adrenal catecholamine content. Consequently, the application of electrical and immobilization stress releases more catecholamines from the adrenal glands of the diazepam-treated rats and also produces higher incidence of ventricular extrasystoles. Furthermore, various pretreatments of rats with diazepam (5-150 mg kg-1 d-1) also lead to an increase in the catecholamine content of the adrenal gland. In diazepam-treated rats, the intravenous administration of ouabain produces a greater release of adrenal catecholamines as well as a greater incidence of cardiac arrhythmias. Several hypotheses are proposed to explain the elevation of adrenal catecholamines and also the higher incidence of ventricular arrhythmias.