ABSTRACT
Dysfunction of the sympathetic nervous system underlies many cardiac diseases and can be assessed by molecular imaging using SPECT tracers as I-metaiodobenzylguanidine (I-MIBG). The norepinephrine analog C-meta-hydroxyephedrine (HED) has been used with PET to map the regional distribution of cardiac sympathetic neurons. Hydroxyephedrine is rapidly transported into sympathetic neurons by the norepinephrine transporter and stored in vesicles. This review describes the mechanism of action, radiosynthesis, and application of HED in the assessment of the cardiac sympathetic nervous system in heart failure, myocardial infarction, and arrhythmias. Noncardiac applications of HED in the clinical setting of sympathetic nervous system tumors and other emerging research applications are described.
Subject(s)
Ephedrine/analogs & derivatives , Positron-Emission Tomography , Radiopharmaceuticals , Sympathetic Nervous System/diagnostic imaging , HumansABSTRACT
Several lines of evidence suggest that novel pharmacological approaches aimed at converting white adipose tissue (WAT) into brown adipose tissue (BAT) may represent an effective therapeutic strategy for obesity and related disorders. ((18))F-fluorodeoxyglucose ((18)F-FDG) is the only positron emission tomography (PET) tracer commonly used to study BAT function, and so far no functional tools have been described to investigate in vivo white-to-brown fat conversion. In this report, we show that the PET tracer (11)C-meta-hydroxyephedrine ((11)C-MHED, a norepinephrine analogue) is a useful tool to investigate the sympathetic nervous system (SNS) activity in BAT of lean and dietary obese mice. Moreover, we demonstrate that (11)C-MHED is a specific marker of the SNS-mediated thermogenesis in typical BAT depots, and that this tracer can detect in vivo WAT to BAT conversion.
