The nicotine patches and gums that have become staples for people who want to quit smoking also show promise in treating people with a variety of brain diseases, researchers told a scientific conference Monday.
They discussed trials of nicotine and related compounds that showed at least some effect on disorders ranging from Tourette's Syndrome and Attention Deficit Hyperactivity Disorder to schizophrenia and depression to Parkinson's and Alzheimer's diseases.
"I think it's safe to say that a number of studies have proved the concept that nicotine can be effective in reducing some of the symptoms of these diseases and perhaps preventing their onset,'' Edward Lloyd, a scientist at The Scripps Research Institute in La Jolla, Calif., told reporters at the annual meeting of the American Association for the Advancement of Science.
"The question now is how we get compounds which will have the same effects without the side effects, particularly the nausea and other intestinal problems, that often accompany nicotine patches,'' said Lloyd, who has been working on Alzheimer's disease.
"We need to refine and focus these drugs and get away from the global, shotgun approaches that we and others have taken with the early research,'' said Paul Sanberg, a neuroscientist at the University of South Florida, Tampa, who has been studying nicotine and related treatments on young patients with Tourette's Syndrome.
Nicotine is the main psychoactive ingredient in tobacco and acts on a number of nerve receptors in the brain that help regulate functions such as movement, concentration and memory. Nicotinic receptors may also help manage the release of brain chemicals that foster the growth of new brain cells.
The brain naturally produces chemicals that send signals to these receptors, but if the receptors or some subset of them malfunction, brain disorders result.
For people who smoke or chew tobacco, some of the receptors set up a pleasurable feedback that encourages them to use more, but no such addiction has been noted among nicotine patch users and rarely for gum chewers, researchers said.
While other studies have suggested that smoking helps protect people from developing Parkinson's, Alzheimer's and schizophrenia, "we're not promoting smoking or tobacco use in any fashion,'' stressed Sanberg.
Researchers also described good early results from several drugs that block the nerves that are sensitive to nicotine. "We think overloading the receptors with nicotine turns down their sensitivity, and blocking them has the same impact,'' Sanberg said.
Tourette's Syndrome is typically treated with a tranquilizing drug called haloperidol, which helps reduce the tics, spastic movements and vocal outbursts common with the condition but often also severely slows down motor function.
Combining low doses of the tranquilizer and a nicotine blocker in a group of 8- to-17-year old Tourette's patients produced "substantial improvement in tics in most patients and substantial improvement in mood and aggressiveness for many,'' Sanberg said.
Dr. Paul Newhouse, an associate professor of psychiatry at the University of Vermont, Burlington, reported nicotine infusions and patches brought both immediate and longer-term improvements in the cognitive and motor skills of a group of patients with mild to moderate Parkinson's disease.
During and just after intravenous doses of nicotine for half an hour, patients showed improvements in attention and arousal, including better reaction time to a stimulus, compared to a control group.
Then the patients wore a nicotine patch for 16 hours a day over two weeks. They showed improvement in measures of motor performance, including standing, walking and sitting, finger dexterity and tests of hand movements.
"Not everyone enjoyed the same level of benefits, but overall the results were pretty positive,'' Newhouse said. "We got one letter from a patient who listed all the benefits he'd seen, including the comment from his wife that he was 'back to his pre-Parkinson's cool self.' ''
Although some of the Vermont patients continued to use over-the-counter nicotine patches after the study ended, Newhouse and other researchers cautioned against people with Parkinson's or other brain disorders from medicating themselves.
"It's still too early to say that they should use it," he said. "We really don't know the long-term effects, and as much as we think that we may have treatment that may work, I just can't recommend it until we've done longer, large-scale clinical trials."
