Regional Uptake of [ 3 H]Norepinephrine by the Canine Left Ventricle 1

Abstract

Abstract

The distribution of sympathetic neurons within the canine left ventricle was assessed by measuring the myocardial uptake of [³H]norepinephrine in anesthetized dogs. The nonneuronal uptake of [³H]norepinephrine was also assessed in a separate group of cocaine-treated animals. The left ventricle was systematically divided into multiple sections. The [³H]norepinephrine was isolated in tissue homogenates, using alumina extraction, and quantified by liquid scintillation counting. The results revealed a nonuniform pattern of [³H]norepinephrine uptake in the ventricular free wall, with a greater uptake in the base than in the apex. Differences in uptake between the anterior and posterior regions of the free wall, and between the free wall and the septum were not statistically significant. In the cocainetreated animals uptake was approximately 20% of that in the control animals. Furthermore, there were no significant regional differences. These data suggest that in the canine left ventricle the sympathetic nerves are distributed nonuniformly between the base and apex, but otherwise the distribution is uniform.