BRS

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BRS Neuroanatomy

Phenylalanine

Phenylalanine hydroxylase

Tyrosine

Tyrosine hydroxylase

L -DOPA

DOPA decarboxylase

Dopamine

Dopamine- b -hydroxylase

Norepinephrine

FIGURE 21.1. Synthesis of catecholamines from phenylal anine. Epinephrine, which is derived from norepinephrine, is found primarily in the suprarenal medulla. DOPA, dihy droxyphenylalanine; l -DOPA, levodopa.

Phenylethanolamine N-methyl transferase

Epinephrine

II. DOPAMINE

A. Characteristics

■ a catecholamine. ■ role in cognitive, motor, and neuroendocrine functions. ■ depleted in Parkinson disease. ■ has increased production in schizophrenia . ■ only found in the central nervous system (CNS). B. Major dopaminergic pathways (Figure 21.2)

Septal nuclei

Dopamine

Nigrostriatal tract

x

e

r t

x

e

r t

c o

c o

t e

u l a

e o

Medial forebrain bundle

n g

Striatum

C i

N

Sup. colliculus

o n t a l

F r

Nucleus accumbens

Mesolimbic tract

Amygdala Entorhinal area

Arcuate nucleus

Substantia nigra Ventral tegmental area

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FIGURE 21.2. Distribution of dopamine-containing neurons and their projections. Two major ascending dopamine path ways arise in the midbrain: the nigrostriatal tract from the substantia nigra and the mesolimbic tract from the ventral tegmental area. In Parkinson disease, loss of dopaminergic neurons occurs in the substantia nigra pars compacta and in the ventral tegmental area.