Noradrenergic

Noradrenergic describes anything relating to the neurotransmitter norepinephrine (also called noradrenaline) and to the nerve cells and pathways that synthesize, release, and respond to it. In the brain, the principal source of noradrenergic neurons is the locus coeruleus, with widespread projections to the cortex, hippocampus, cerebellum, brainstem, and spinal cord. These pathways modulate arousal, attention, learning, memory, mood, and the stress response, and they influence other neurotransmitter systems.

In the peripheral nervous system, most postganglionic sympathetic neurons release norepinephrine at target organs, producing effects such as increased heart rate, vascular tone, and energy mobilization. Sweat glands are an exception, receiving acetylcholine from sympathetic fibers.

Noradrenergic signaling is mediated by adrenergic receptors, including alpha-1, alpha-2, beta-1, beta-2, and beta-3 receptors. Norepinephrine has varying affinities for these receptors, and receptor activation underlies physiological responses. Termination of signaling occurs mainly through reuptake by the norepinephrine transporter (NET), with subsequent metabolism by monoamine oxidase and catechol-O-methyltransferase.

Pharmacologically, noradrenergic function can be augmented or diminished by drugs such as norepinephrine reuptake inhibitors (e.g., atomoxetine, reboxetine, certain SNRIs), monoamine oxidase inhibitors, and receptor agonists/antagonists. Clinically, altered noradrenergic function is associated with mood disorders, attention deficits, anxiety, PTSD, and hypertension, among others.