92 • Alternatives to Animal Use in Research, Testing, and Education 
pressure has been monitored for 5 years; this per- 
mits the study of high blood pressure in parents, 
offspring, and future generations to analyze the 
tendency to inherit the condition. 
Parkinson's Disease 
Parkinson's disease is a neurological disorder 
of older adults characterized by palsy and rigid 
muscles. Progress in understanding the cause and 
development of the disease and in refining meth- 
ods of long-term drug therapy has been ham- 
pered by lack of an adequate animal model. At- 
tempts to induce the disease in rats, guinea pigs, 
and cats either have failed to produce all the 
symptoms or have yielded symptoms that do not 
last long and so cannot be effectively researched. 
In 1983, the first animal model of Parkinson’s 
disease was developed. Scientists at the National 
Institute of Mental Health (NIMH) induced a form 
of parkinsonism in eight rhesus monkeys by giv- 
ing them a drug, l-methyl-4-phenyl-l,2,3,6-tetra- 
hydropyridine (MPTP), that selectively destroys 
specific cells in the substantia nigra, a region of 
the brain destroyed in humans by Parkinson’s dis- 
ease. The monkeys exhibited all the major clini- 
cal features of Parkinson’s disease in humans. 
They also responded dramatically to L-dopa, the 
standard medication for people with this disease 
(8). NIMH researchers have speculated that the 
availability of this new animal model may lead to 
understanding the reason Parkinson’s disease oc- 
curs in older adults, the course of the disease, and 
drug therapy and its side effects (30). 
In 1984, squirrel monkeys were used to shed 
further light on the mechanism of MPTP -induced 
parkinsonism. Pargyline, a drug currently pre- 
scribed for high blood pressure in humans (Eu- 
tonyl, Abbott Laboratories, North Chicago, IL), 
was used to prevent the neurotoxic effects of 
MPTP (31). These results in squirrel monkeys sug- 
gested that MPTP itself may not be the actual neu- 
rotoxic agent. Instead, attention is now focused 
on an MPTP metabolite and on the mechanism 
of MPTP metabolism in the brain (33). 
Baldness 
Like many men, stumptail monkeys become 
bald as they age. This trait has made the stump - 
tail monkey the animal of choice in baldness 
research. Although it is not life-threatening, bald- 
ness is a matter of concern for many people: Hair- 
combing patterns suggest that many men desire 
to have hair where there is none, and advertise- 
ments for hair restoration abound in the popular 
media. The public spends large sums on hair- 
restoration nostrums, and in 1985 the FDA pro- 
posed banning the sale of all nonprescription drug 
products sold to prevent or reverse baldness, hav- 
ing concluded there is no scientific evidence that 
such lotions and creams are effective (50 FR 2191). 
A drug originally developed to manage high 
blood pressure, minoxidil, has the unexpected 
side effect of causing thick hair growth from fol- 
licles that normally produce only fine, downy 
hair. To test the potential of minoxidil for hair 
growth, researchers applied it externally to the 
bald front scalp of stumptail monkeys. The results 
with monkeys showed promise, and clinical trials 
are now in progress with bald men across the 
United States. Monkey studies are continuing to 
assess the effects and safety of minoxidil as a 
means of counteracting hair loss. 
Menopausal Hot Flashes 
Of the 30 million postmenopausal women in the 
United States, as many as 75 percent have ex- 
perienced or will experience hot flashes brought 
on by increased blood flow to the skin. Hot flashes 
produce a feeling of warmth for several minutes, 
and they are often followed by sweating. These 
physical symptoms may be accompanied by ner- 
vousness, irritability, and depression. At present, 
physicians can treat the symptoms of menopause, 
but the causes of the symptoms remain unknown. 
Research into the mechanisms of menopause and 
the development of therapy for menopausal 
problems has been hampered by the difficulty of 
studying this condition in animals. This difficulty 
stems from three facts: Only primates, and no 
other nonhuman species, have menstrual cycles; 
monkeys do not exhibit symptoms of menopause 
until at least age 25; and monkeys brought into 
the laboratory from the wild are rarely of meno- 
pausal age. 
Throughout the last decade, researchers have 
studied the menstrual cycle and its cessation in 
