Publisher Summary Recent research related to catecholamines in the periphery has dealt with assessment of peripheral catecholaminergic function, catecholamines and stress, catecholamines and pain, catecholamines and neuroimmunology, adrenomedullary secretion and cosecretion, neurocardiology, catecholamines and metabolism, and roles of catecholamines in the brain in regulation of the cardiovascular system. All of these are discussed in this chapter. Peripheral catecholaminergic systems probably play a role in many neurocardiologic disorders, either secondarily as homeostatic effectors or primarily as etiologic factors. The hemodynamic hallmark of neurocardiogenic syncope is systemic vasodilation, with or without bradycardia. The vasodilation results from sudden, marked decreases in sympathoneural outflows. In contrast, plasma epinephrine (Epi) levels generally increase in this setting. Studies show a close association between lymphocyte concentrations of catecholamines and of cyclic adenosine monophosphate (cAMP). The usefulness of lymphocyte norepinephrine (NE) concentrations in evaluating sympathoneural function remains unknown. Studies using microdialysis, specific activity of [ 3 H]normetanephrine, and NE concentrations in lymph is likely to enable estimates of NE concentrations in interstitial fluid and, thereby, estimates of release of NE from sympathetic nerves. More convincing, consistent evidence is required to understand the role of catecholaminergic systems in components of immune responses. Increased use of microdialysis in adipose tissue and skeletal muscle is likely to enhance understanding of catecholaminergic systems in patients with a variety of metabolic disorders, including insulin-dependent diabetes mellitus (IDDM) and obesity.