Cardiac Catecholamines in Rabbits: Seasonal Changes and Norepinephrine Effect

In an attempt to determine whether myocardial catecholamines vary from season to season, their concentration in rabbits was measured throughout the whole year by the spectrophotofluorometric method. The highest concentration of cardiac catecholamine was observed in summer. Measurement of the atrial response to norepinephrine revealed no significant alteration during the entire period of the experiment.