Norepinephrine NE neurotransmitters formation start with the uptake of tyrosine into the cytoplasm. Dopamine is transformed into dopa then to dopamine which converted in the storage vesicles into norepinephrine. NE is metabolized in synaptic cleft by COMT

Dopaminergic innervation is under tight control in the nervous system. A decrease in dopaminergic innervation results in development of Parkinson disease, whereas elevation of dopaminergic activity may results in Psychotic disorders such as schizophrenia

The main target of antiparkinsonian drugs is to increase the dopamine concentration and activity in the brain. Levodopa is transformed into dopamine in the brain, DDC and COMT inhibitors decrease the peripheral metabolism of levodopa. Dopamine agonists a