Noradrenaline
| adrenal medulla | |
| amino acid derivative | |
| α and β receptors |
Noradrenaline' (also norepinephrine) is a hormone produced by the adrenal medulla and a neurotransmitter. It is particularly involved in the activities of the sympathetic vegetative system and in mediating the stress response.
It is stored and synthesized (mainly) in the terminal branches of unmyelinated 'sympathetic postganglionic nerve fibers. After action potential is received, there is an influx of Ca2+ and an outpouring of noradrenaline into the synaptic cleft.
Synthesis
Biosynthesis takes place in the adrenal medulla and adrenergic neurons. The basis is tyrosine.
- Dopa - hydroxylation of the aromatic ring, tetrahydrobiopterin (THB);
- Dopamine - dopa decarboxylation, pyridoxal phosphate;
- Noradrenaline - hydroxylation of dopamine, dopamine-β-monooxygenase (cofactor: ascorbic acid).
Effect
It works by binding to the adrenergic receptor system G-proteins.
Increasing inotropy
bathmotropia, chronotropia and dromotropia
The mechanism of increased contraction works thanks to β1- receptors on the myocardial membrane, which bind noradrenaline and cause an increase in cAMP concentration, which activates protein kinase, which phosphorylates L-type Ca²+ channels, which thereby remain open longer.
For more information see Catecholamines.
