Increase in myocardial interstitial norepinephrine during a short period of coronary occlusion

The neurally intact in vivo beating hearts of cats were used to examine the influence of a short period of coronary occlusion on regional myocardial norepinephrine levels. Using a cardiac dialysis technique, dialysate norepinephrine levels were measured as an index of myocardial interstitial norepinephrine levels, and the left anterior descending coronary artery was occluded for 10 min. In anesthetized cats, 10 min occlusion increased the dialysate norepinephrine level in the ischemic region but not in the non-ischemic region. To investigate the influence of neuronal norepinephrine uptake on occlusion-induced dialysate norepinephrine response, a neuronal uptake inhibitor (desipramine) was locally administered to both regions with the dialysis perfusate. In the ischemic region, 10 min occlusion significantly increased the dialysate norepinephrine level from the control level in the presence of desipramine. We concluded that 10 min coronary occlusion was associated with an increase in the myocardial interstitial norepinephrine level in the ischemic region. This increase in the early phase of ischemia was not attributed to attenuation of neuronal norepinephrine uptake function.