Disease. The basic pathologic change is degeneration of a group of nerve cells deep within the center of the brain in an area called the substantia nigra. These cells use dopamine as their neurotransmitter to signal other nerve cells. As these cells degenerate and stop functioning, dopamine fails to reach the areas of the brain that affect motor functions. The possible role of toxins in the disease process has aroused considerable interest. See also dopamine. Therapy for parkinson's disease is aimed at replacing dopamine. Since the blood-brain barrier prevents dopamine from entering the brain from the bloodstream, a precursor of dopamine (l-dopa) that will enter the brain is given. L-dopa is usually administered as part of a compound that inhibits the enzymes that break down l-dopa in the liver, thus making a greater part of it available to the brain. See also motor systems; nervous system (vertebrate); sensation. Columbia encyclopedia: parkinson's disease top home > library > miscellaneous > columbia encyclopedia parkinson's disease or parkinsonism, degenerative brain disorder first described by the english surgeon james parkinson in 1817. When there is no known cause, the disease usually appears after age 40 and is referred to as parkinson's disease; a number of genes have been found to be associated with the disease. cheap viagra Parkinsonism usually refers to similar symptoms resulting from head injury, encephalitis, syphilis, carbon monoxide poisoning, cerebral arteriosclerosis, or use of mptp (a synthetic narcotic). The disorder is also termed paralysis agitans, or shaking palsy. Parkinson's disease is a debilitating and progressive disorder in which the chemicals that facilitate electrical transmission between nerve cells are depleted. It was the first disease to be treated by drugs that replace deficient neurotransmitters. buy viagra cheap Symptoms usually begin in middle to later life with trembling of the lips and hands, loss of facial expression, and muscular rigidity. liquid viagra when to take As it progresses it may bring on body tremors, particularly in muscles at rest. generic viagra canada Movements become slow and difficult; walking degrades to a shuffle. cheap generic viagra After many years physical incapacity may occur. Dementia occurs in at least 50% of the patients; depression is also common. When drugs such as levodopa (l-dopa) are taken orally, many of the worst symptoms are lessened. viagra pills canada cheap New drugs such as pramipexole (mirapex) and ropinirole (requip) can delay the need for levodopa. Apomorphine (apokyn) is used treat episodes of reduced mobility in patients with advanced parkinson's that responds less effectively to levodopa. cheap pills viagra Future approaches to treatment include a focus on early detection and slowing progression of the disease. is 200 mg of viagra too much Encouraging results have been reported from surgical insertion of a pacemakerlike device deep in the brain to s. viagra gold reviews