Neurotransmitters are vital components of the nervous system. The human nervous
system comprises more than 40 transmitters. A few of the most significant neurotransmitters
include dopamine, gamma-aminobutyric, acetylcholine, serotonin, glutamate, histamine, and
norepinephrine. Norepinephrine serves a critical role in helping the body adjust to various
Also known as noradrenaline, norepinephrine is an excitatory neurotransmitter that
primarily emerges from sympathetic nerve fibres ends (Schwarz & Luo, 2015). The primary
functions of norepinephrine encompass increasing the force of skeletal muscle contracts and
regulating the contraction force and rate of the heart. This regulation is critical to prepare the
body to react or retreat in the instance of acute danger. Brainstem norepinephrine comprises a
tiny but diverse population of cells that project across all central nervous system parts.
The primary noradrenergic nucleus of the brain is locus coeruleus (LC). The numerous
fibre projecting across the neuraxis originate from the LC. The LC is a significant arousal-
promoting nucleus that emerges from the excitatory projections to most of the cerebral cortex,
substantial inhibitory projections, cholinergic neurons, cortically projecting neurons, and
serotoninergic neurons (Robertson et al., 2016). The function of the LC is regulating the
autonomic functions. These functions emerge from two primary forms. One projects directly to
the spinal cord while the second projects to the autonomic nuclei. Prominent autonomic nuclei
comprise salivatory nuclei, dorsal motor nuclei, and rostoventrolateral medulla. Others include
amygdala, nucleus ambiguous, and Edinger-Westphal nucleus.
The activity of norepinephrine neurons plays a critical role in numerous behavioral and
physiological processes such as arousal, mood, attention, appetite, memory, and homeostasis.
The functional diversity of norepinephrine varies with the anatomical location, response to
conditions, connectivity, and environmental factors. Molecular markers determine the functional
diversity and can differentiate functionally unique sub-populations of noradrenaline. The
information is critical to inform the understanding of norepinephrine vulnerability to disease and
environmental factors besides providing access to specific norepinephrine neurons sub-
population for research.
Robertson, S. D., Plummer, N. W., & Jensen, P. (2016). Uncovering diversity in the
development of central noradrenergic neurons and their efferents. Brain Research, 1641,
Schwarz, L. A., & Luo, L. (2015). Organization of the locus coeruleus-norepinephrine
system. Current Biology, 25(21), R1051-