ELEVATION OF EITHER AXOPLASMIC NOREPINEPHRINE OR SODIUM-LEVEL INDUCEDRELEASE OF NOREPINEPHRINE FROM CARDIAC SYMPATHETIC-NERVE TERMINALS

Using dialysis technique, prominent accumulation of norepinephrine (NE ) in the myocardial interstitial space was observed under two differen t conditions: (I) local administration of a monoamine oxidase inhibito r (pargyline, 1, 10 mM), (2) local administration of a Na,K-ATPase inh ibitor(ouabain, 10, 100 mu M). Further, pretreatment with a vesicle up take inhibitor (reserpine, 10 mu M) augmented these responses. Either condition independently caused endogenous NE release and a brisk incre ase in dialysate NE levels might occur as a a consequence of non-exocy totic release of NE.