Scientists at the University of Florida and Lund University in Sweden
have reversed some of the effects of Parkinson's disease, a condition
caused by the loss of dopamine-producing brain cells, in rats with a
chemically induced form of the disease. Dopamine is a brain chemical
called a neurotransmitter that allows signals to travel along nerve
cells.

By inserting corrective genes into the brains of rats, researchers
were able regrow an important bundle of nerve fibers, according to a
report in the April 2, 2002, issue of the Proceedings of the National
Academy of Sciences.

The new nerve growth was linked to significant, but not complete,
recovery of the animals' ability to use their paws spontaneously,
said Ronald J. Mandel, a University of Florida scientist who was part
of the team and a coauthor of the report.

The gene therapy experiments were conducted at Lund University in
Sweden, where Mandel was a visiting scientist. In addition to Mandel,
the scientists included Anders Bjorklund, a pioneer in the
transplantation of stem cells into the brains of patients with
Parkinson's disease.

The researchers inserted copies of a gene to produce a specific
protein in the brains of laboratory rats. The protein, known as GDNF,
helps in the normal development of dopamine cells and the fibers that
connect them to another part of the brain -- the striatum in the
forebrain.

The corrective genes were placed either in the substantia nigra, the
part of the brain where the dopamine neurons are found, or in the
striatum. In a third group, they were inserted in both areas.

Four weeks after inserting the genes, the researchers induced a rat
version of Parkinson's disease by injecting a drug to destroy the
dopamine cells. The gene therapy treatment protected some rats
against the drug and in others enhanced recovery from damage the drug
did cause.

Only the rats that received the treatment exclusively in the striatum
improved, Mandel said, and the effects lasted through the 6 months of
the experiment.

The scientists said that this strategy that proved effective in rats
is not a cure for Parkinson's disease, but they hope it will lead to
a better method for delaying and controlling symptoms of the
progressively disabling condition in humans.

Mandel said the effectiveness of gene therapy in the Parkinsonian
rats generates hope that the therapy can eventually be applied in
humans, with the potential to double the time a person with
Parkinson's disease will respond well to standard medications.

By Darrin Kiessling