In vivo and in vitro studies on the effect of tetrahydropapaveroline and salsolinol on COMT and MAO activity in rat brain.

Studies were made on COMT and MAO activity in rats 2, 4, 6, 12 and 24 h after intraperitoneal treatment with 8 and 60 mg/kg doses of tetrahydropapaveroline (THP), and 10 and 20 days after treatment with 8 mg/kg/day. Results suggested COMT activity inhibition only after 2 h of treatment. Experiments were also performed on THP and salsolinol methylation capacity in vitro. Results showed that both alkaloids use COMT enzymes for methylation and can also act as competitive inhibitors of COMT and MAO activity.