Carlsson wondered if reserpine also decreased dopamine. He injected the drug into rabbits and found that it makes them listless; their ears droop and they can’t move. In an attempt to counteract these effects, he injected the chemical precursor of serotonin into the rabbits. Nothing happened. He then injected the precursor of dopamine, L-dopa, and behold, the animals woke up. Carlsson recognized the importance of his finding, and in 1958 he proposed that dopamine is somehow involved in Parkinson’s disease.
