NEURONAL RELEASE OF ADRENALINE BY TRANSMURAL FIELD STIMULATION OF THEATLANTIC SALMON (SALMO-SALAR) CARDIAC ATRIUM

1. The atrial cardiac tissue of the Atlantic salmon was pre-incubated with H-3-adrenaline before transmural electrical field stimulation at 8-degrees-C in vitro. 2. The total contractile tension response and th e total H-3-release, but not the net H-3-release per pulse, increased in proportion to the stimulus frequency from 1 to 4 Hz. These response s were nearly abolished by guanethidine and counteracted by propranolo l. 3. The results indicate that in vitro accumulated adrenaline was re leased from a neuronal pool activating atrial contractility via beta-a drenoceptors, and are consistent with our hypothesis of a neuronal upt ake of plasma adrenaline for re-use as neurotransmitter during and fol lowing periods of stress.