Effects of active chronic cocaine use on cardiac sympathetic neuronal function assessed by carbon-11-hydroxyephedrine

Abstract

Cardiac toxicity of cocaine has been linked to its inhibitory effect on norepinephrine reuptake by sympathetic nerve terminals of the heart. Carbon-11-hydroxyephedrine is a positron-emitting tracer that has been validated as a highly specific marker for norepinephrine transporter activity of the sympathetic nerve terminals and thus makes possible in vivo assessment of the effect of cocaine on norepinephrine reuptake and storage in the cardiac sympathetic nerve terminals. The aim of the study was to use the catecholamine analog 11C-hydroxyephedrine with PET to determine whether active chronic use of cocaine in women modifies the function of sympathetic nerve terminals of the heart.

Methods: Six normal female volunteers and nine female active chronic cocaine users were studied. Cardiac regional 11C-hydroxyephedrine uptake and blood flow, as assessed with 13N-ammonia, were determined using semi-quantitative polar map analysis of myocardial tracer distribution. Carbon-11-hydroxyephedrine cardiac retention was quantified using dynamic data acquisition and kinetic analysis of blood and tissue activity.

Results: Active chronic cocaine users showed small areas of abnormal blood flow and 11C-hydroxyephedrine retention in the heart in comparison with normal volunteers. The extent of abnormalities expressed as a percent of the total polar map area averaged 2.0% +/- 2.6% and 2.5% +/- 2.7% for blood flow and 11C-hydroxyephedrine uptake, respectively. Myocardial 11C-hydroxyephedrine retention was significantly reduced by 22% in active cocaine users (0.109 +/- 0.017 min-1), as compared to normal controls (0.140 +/- 0.027 min-1).

Conclusion: PET imaging with 11C-hydroxyephedrine permits quantitative assessment of cardiac norepinephrine transporter function in active chronic cocaine users. The results of this study suggest prolonged reduction of norepinephrine uptake and storage capacity in the cardiac sympathetic nerve terminals which may reflect the effect of repetitive elevation of norepinephrine levels induced by cocaine exposure.