正腎上腺素

正腎上腺素是一種拟正交感神经素(catecholamine)和phenethylamine，它的化學結構為：C₈H₁₁NO₃。它由腎上腺生產，以荷爾蒙的形式進入血液, but it is also a neurotransmitter in the nervous system where it is released from noradrenergic neurons during synaptic transmission. It is one of the 'stress hormones' and affects parts of the human brain where attention and impulsivity are controlled. This compound affects the fight-or-flight response, activating the sympathetic nervous system to directly increase heart rate, release energy from fat and increase muscle readiness.

The host of physiological changes activated by a stressful event are unleashed in part by activation of a nucleus in the brain stem called the locus ceruleus. This nucleus is the origin of most norepinephrine pathways in the brain. Neurons using norepinephrine as their neurotransmitter project bilaterally from the locus ceruleus along distinct pathways to the cerebral cortex, limbic system, and the spinal cord, among other projections.

[编辑] 合成方式

Norepinephrine is synthesized by a series of enzymatic step in the adrenal medulla from the amino acid tyrosine. The first reaction is the oxidation into Dihydroxyphenylalanine (L-DOPA), followed by decarboxylation into the neurotransmitter dopamine, and the final β-oxidation into norepinephrine. Norepinephrine can be further methylated to epinephrine (called adrenaline outside the USA).

[编辑] 外部連結

• http://www.surgeongeneral.gov/library/mentalhealth/chapter4/sec2_1.html