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The adrenal glands are key components of the mammalian endocrine system and comprise two morphologically and functionally distinct regions, the outer adrenal cortex and inner adrenal medulla. The medulla is populated with neural crest-derived adrenal chromaffin cells that function as the neuroendocrine arm of the sympathetic nervous system. Upon stimulation, chromaffin cells secrete catecholamines (epinephrine and norepinephrine) and neuropeptides into the bloodstream to coordinate the physiologic responses to environmental, metabolic, and emotional/psychologic stressors. This chapter summarizes current knowledge pertaining to the synthesis, storage, and secretion of catecholamines from adrenal chromaffin cells. Catecholamines exert widespread effects mediated by a family of cognate G protein–coupled receptors (adrenoceptors) that recruit diverse cellular signaling pathways. These physiologic effects are discussed along with some maladaptive responses to catecholamines that lead to stress-related pathophysiologic states. |
