Psychomotor, neuroendocrine and behavioural effects after oral administration of levodopa in normal volunteers.

The oral administration of a single dose of levodopa (L-dopa) in 10 healthy human male subjects induced cognitive, not motor, changes during figure-copying tasks that were unrelated to the neuroendocrine and behavioural effects of levodopa. Results point to a decrease in alertness induced by levodopa.