The Journal of Neuroscience, March 1, 2003, 23(5):1974
Glial Cell Line-Derived Neurotrophic Factor Increases
Stimulus-Evoked Dopamine Release and Motor Speed in Aged Rhesus Monkeys
Richard
Grondin*,
Wayne A.
Cass*,
Zhiming
Zhang,
John A.
Stanford,
Don M.
Gash, and
Greg
A.
Gerhardt
Department of Anatomy and Neurobiology and Morris K. Udall
Parkinson's Disease Research Center of Excellence, University of
Kentucky Medical Center, Lexington, Kentucky 40536-0298
Changes in the functional dynamics of dopamine release and
regulation in the basal ganglia have been posited to contribute to
age-related slowing of motor functions. Here, we report the effects of
glial cell line-derived neurotrophic factor (GDNF) on the
stimulus-evoked release of dopamine and motor speed in aged monkeys
(21-27 years of age; n = 10). Although no changes were observed in the vehicle controls (n = 5),
chronic infusions of 7.5 µg of GDNF per day for 2 months into the
right lateral ventricle initially increased hand movement speed up to
40% on an automated hand-reach task. These effects were maintained for at least 2 months after replacing GDNF with vehicle, and increased up
to another 10% after the reinstatement of GDNF treatment for 1 month.
In addition, upper-limb motor performance times of the aged
GDNF-treated animals (n = 5) recorded at the end of
the study were similar to those of five young adult monkeys (8-12
years of age). The stimulus-evoked release of dopamine was
significantly increased, up to 130% in the right caudate nucleus and
putamen and up to 116% in both the right and left substantia nigra of the aged GDNF recipients compared with vehicle controls. Also, basal
extracellular levels of dopamine were bilaterally increased, up to
163% in the substantia nigra of the aged GDNF-treated animals. The
data suggest that the effects of GDNF on the release of dopamine in the
basal ganglia may be responsible for the improvements in motor
functions and support the hypothesis that functional changes in
dopamine release may contribute to motor dysfunctions characterizing senescence.
Key words:
chronic GDNF; aging; rhesus monkeys; in
vivo microdialysis; basal ganglia; motor speed
*
R.G. and W.A.C. contributed equally to this work.