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-- [ From: Donna Kipp * EMC.Ver #2.10P ] -- 4:01 PM (ET) 3/20 Injections Ease Parkinson's NEW YORK (AP) -- Monkeys got significant relief from Parkinson's disease symptoms when a natural substance was injected into their brains -- a hopeful sign for developing a new treatment. Tests on human Parkinson's patients are expected to begin this year. Parkinson's affects some 500,000 to 1 million Americans, causing such difficulties as slowed movement, rigidity and tremors. The work in rhesus monkeys was reported in Thursday's issue of the journal Nature by Don Gash and colleagues at the University of Kentucky College of Medicine in Lexington, with scientists at Amgen Inc. of Thousand Oaks, Calif., and researchers elsewhere. Amgen, which is planning the initial human experiments to study safety and side effects, helped pay for the monkey work. ``It's a very important demonstration,'' said Dr. Serge Przedborski, assistant professor of neurology at the Columbia University College of Physicians and Surgeons in New York. He cautioned, however, that some major questions about potential usefulness in people have yet to be answered. The injected substance is called GDNF. It's found naturally in the brain, where it appears to be involved in normal development, Gash said. The experiments used much higher levels of GDNF than are normally found in the mature brain. Scientists used monkeys that had been injected with a toxin that damaged one side of their brains, producing Parkinson symptoms on one side of the body. The researchers injected GDNF into the affected side of the brain. A single injection produced improvement within two weeks, and it persisted for at least four weeks. When animals were repeatedly injected, once every four weeks, the improvement was maintained for the 12 weeks of the experiment. The GDNF reduced the problems of slow movement, arm and leg rigidity and poor balance by at least about 25 percent. There was no significant reduction in tremors, which Gash called a surprise. Maybe the tremors were produced by different brain circuits than those producing the other symptoms, he said. The only side effect was weight loss of up to 10 percent, which was recovered by the fourth week of treatment. Parkinson's is caused by a deficiency of dopamine, which brain cells use to communicate, in key areas of the brain. GDNF makes brain cells pump out more dopamine, Gash said. It may also help by letting brain cells better regulate their release and retrieval of dopamine, so that the short supply doesn't go to waste, he said. Przedborski said scientists must learn more about how GDNF reduces Parkinson symptoms before designing human treatments, because the biochemical findings in the monkeys' brains included a puzzling result: GDNF did not increase dopamine levels in the parts of the brain where dopamine produces its effect on movement. Gash said he believes GDNF's benefit there came from better regulation of dopamine, but that remains to be proved. Przedborski also said it will be important to find out how long the benefits of a single GDNF injection last and whether they dissipate over a long time with repeated injections. GDNF stands for glial-cell-line-derived neurotrophic factor. News or information from AP may not be published, broadcast or redistributed without the prior written authorization of AP. Copyright 1996 The Associated Press. All Rights Reserved.