noradrenergic system

Noradrenergic system

A neuronal system that is responsible for the synthesis, storage, and release of the neurotransmitter norepinephrine. Norepinephrine, also known as noradrenalin, consists of a single amine group and a catechol nucleus (a benzene ring with two hydroxyl groups) and is therefore referred to as a monoamine or catecholamine. It exists in both the central and peripheral nervous systems. Norepinephrine is the primary neurotransmitter released by the sympathetic nervous system, which mediates the “fight or flight” reaction, preparing the body for action by affecting cardiovascular function, gastrointestinal motility and secretion, bronchiole dilation, glucose metabolism, and so on. Within the central nervous system, norepinephrine has been associated with several brain functions, including sleep, memory, learning, and emotions.

After synthesis, the majority of norepinephrine is transported into synaptic vesicles in the nerve terminals, where it remains until needed. When the nerve terminal is activated by depolarization, calcium flows into it, leading to the release of norepinephrine into the synaptic cleft. Once released into the synaptic cleft, norepinephrine is free to bind to specific receptors located on the presynaptic or postsynaptic terminal, which initiates a chain of events (the effector system) in the target cell that can be mediated by a number of different second messenger systems. The exact effect is determined by the identity of the receptor activated. See Epinephrine, Second messenger, Sympathetic nervous system, Synaptic transmission

Termination of norepinephrine occurs by a reuptake mechanism in the presynaptic membrane. Once transported back into the presynaptic terminal, norepinephrine can be stored in vesicles for future use or enzymatically degraded by monoamine oxidase.

Certain medications achieve their effect by altering various stages of synthesis, storage, release, and inactivation of norepinephrine. The behavioral manifestations of these alterations have led to a better understanding of norepinephrine's role in various psychiatric disorders. See Affective disorders, Monoamine oxidase, Psychopharmacology, Schizophrenia, Stress

noradrenergic system

[nȯr¦ad·rə¦nər·jik ′sis·təm]
(neuroscience)
A system of neurons that is responsible for the synthesis, storage, and release of the neurotransmitter norepinephrine.
References in periodicals archive ?
Noradrenergic system seems to be less affected in suicidal behavior.
For example, exposure to extreme cold produces a marked activation of the sympathetic noradrenergic system in an effort to regulate core body temperature, yet it has minimal effects on the endocrine or hormonal stress response (Goldstein and Kopin 2007).
The noradrenergic system is crucial in the pathophysiology of depression (George et al.
Together with clinical reports, "these data provide the basis for REM sleep dysregulation as a core feature in PTSD," whereby increased activity in the amygdala and decreased inhibitory input from the medial prefrontal cortex lead to a persistently overactive noradrenergic system.
Hypocretin (orexin) activation and synaptic innervation of the locus coeruleus noradrenergic system.
A major target of the noradrenergic system is the hippocampus, a region that is critical for learning and memory.
McIntosh and Barfield (1984a) found that the central dopaminergic pathways are important aspects of a normal post-ejaculatory refractory period in male rats and also that the noradrenergic system is essential for normal male rat copulatory behaviour (McIntosh & Barfield, 1984b).
The amygdala also projects to various arousal networks like the basal forebrain cholinergic system, the brainstem cholinergic system and the locus coeruleus noradrenergic system.
Therefore, these results suggest the involvement of the noradrenergic system in the development of tolerance.
Stress in general, and PTSD, in particular, is thought to be associated with activation of the noradrenergic system (NAS).
Nicotine exposure could alter appetite-regulating neural systems in the brain as well as the peripheral noradrenergic system, which is involved in metabolic control over adipose tissue.
In contrast, an overactive noradrenergic system without activation of the dopaminergi c system may lead to depression.