Answer
Answer 18-5. Parkinson's symptoms are due to deficient dopamine effects in the basal gangia. Acetylcholine and dopamine have opposite effects in the basal ganglia. Therefore, agonists of dopamine and blockers of acetylcholine are use to treat it. The most common treatment is levodopa, which crosses the blood-brain barrier (while dopamine can not). Carbidopa is needed to block dopa decarboxylase, preventing generation of peripheral dopamine from levodopa, limiting side effects. Direct dopamine agonists are used as are some inhibitors of dopamine enzymatic degradation. Cholinergic blocking agents may help some patients.