Short- and long-term effects of L-dopa administration on striatal acetylcholinesterase activity

Exogenously applied dopamine may interfere with cholinergic activity in the brain. The aim of the present work was to study the effect of L-dopa administration on acetylcholinesterase (EC 3.1.1.7) activity in rat (Wistar) brain striatum. Short-term administration of a mixture of L-dopa (10 mg/kg) and carbidopa (1 mg/kg) resulted in an increase in dopamine content and a decrease in acetylcholinesterase activity of the tissue. The greatest changes were found 30 min postinjection, and activity returned to near-control values after 2 h. When the drug mixture was injected for a period of 30 d and the animals were killed 24 h after the last injection, a lower dopamine content and higher enzyme activity were seen, compared to control values. It would appear that chronic administration of L-dopa gradually reduced the dopamine-storage capacity of the striatum and that the activity of acetylcholinesterase might be controlled by the levels of dopamine in the brain striatum.