Cardiac receptor physiology and its application to clinical imaging: present and future

Both gamma imaging and positron emission tomography (PET) imaging of cell surface receptors have become possible through the development of agonists and antagonists with high specific radioactivity and high specificity for the receptors. An understanding of the physiology of the cardiac receptor system is essential to comprehending receptor imaging. The complexity of the physiologic information developed over the past decade has been compounded by the concomitant discovery of additional receptor subtypes. The following is a review of a select group of cardiac receptors and their regulation-namely, adrenergic, muscarinic-cholinergic, adenosine, and angiotensin I and II receptors. The role of imaging regional receptor localization and function in providing new insights into cardiac pathology and therapeutic avenues is explored.