Norepinephrine and Epinephrine: Introduction

Abstract

The catecholamines, norepinephrine and epinephrine (formerly named noradrenaline and adrenaline) are released from the adrenal gland and neurons in the brain. Norepinephrine is also released from the majority of postganglionic, sympathetic neurons in the peripheral (autonomic) nervous system. Conversion of the amino acid, tyrosine, to l ‐3,4‐dihydroxyphenylalanine is the rate‐limiting step in the synthetic pathway for both these catecholamines. This process is regulated by several hormones and neurotransmitters, which act via intracellular messengers to help ensure that the rate of catecholamine synthesis matches the rate of their release. In the periphery, norepinephrine and epinephrine are essential for maintaining a stable internal body state (‘homoeostasis’). In the central nervous system, norepinephrine has an important role in the regulation of attention/vigilance/alarm and its synchronization with the autonomic nervous system, but little is known about the function of neuronal epinephrine. Key Concepts The distribution of norepinephrine and epinephrine in the periphery. The distribution of norepinephrine and epinephrine in and brain. Regulation of the biosynthesis of norepinephrine and epinephrine. The role of norepinephrine and epinephrine in the periphery. The role(s) of norepinephrine and epinephrine in the brain.