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—degenerate in Huntington's diseas e.
3. Dopamine-containing neurons (see Figure 22-2)
-are found in the pars compacta of the substantia nigra.
-give rise to the dopaminergic nigrostriatal projectio n.
-are thought to regulate the production of striatal peptides and pept ide
mRNA. -degenerate in Parkinson's
4. Acetylcholine (ACh)-containing neurons (see Figure 22-1)
-are local circuit neurons found in the striatum.
5. Neuropeptide-containing neurons (see Figures 22-6 to 22-8)
-include enkephalin, dynorphin, substance P, somatostatin,
neurotensin, neuropeptide Y, and cholecystokinin.
-are also found in the basal ganglia.
-coexist with the major neurotransmitters (e.g., GABA and/or
enkephalin and GABA and/or substance P).
D. Clinical considerations
1. Parkinson's disease
-is a common condition that is associated with degeneration and depig-
mentation of neurons in the substantia nigra.
-results in the depletion of dopamine in the caudate nucleus and
-includes clinical manifestations of hypokinesia and bradykinesia
(difficulty in initiating and performing volitional movements); rigid-
ity (cog-wheel and lead-pipe rigidity); and resting tremor (pill-
2. MPTP-induced parkinsonism
-is caused by MPTP (l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine), a
meperidine analog found in illicit recreational drugs.
—results in the destruction of dopaminergic neurons, which are located
in the substantia nigra.
3. Huntington's disease (chorea major)
-is an inherited autosomal dominant movement disorder associ-
ated with severe degeneration of the cholinergic and GABA-ergic neu-
rons, which are located in the caudate nucleus and putam en.
-is usually accompanied by gyral atrophy in the frontal and temporal
-can be traced to a single gene defect on chromosom e 4.
Chapter 21 Basal Ganglia and the Striatal Motor System I 323
-results in clinical manifestations of choreiform movements and
progressive dementia. -results in hydrocephalus ex vacuo,
due to the loss of neurons
located in the head of the caudate nucleus, and to a lesser extent in
the putamen. —prenatal and postnatal diagnosis is available with DNA
4. Other choreiform dyskinesias
a. Sydenham's chorea (St. Vitus' dance)
-is overall the most common cause of chor ea.
-occurs mainly in girls as a sequela to rheumatic fev er.
b. Chorea gravidarum