INHIBITION OF BRAIN MONOAMINE-OXIDASE BY ADDUCTS OF 1,2,3,4-TETRAHYDROISOQUINOLINE WITH COMPONENTS OF CIGARETTE-SMOKE

A series of adducts of 1,2,3,4-tetrahydroisoquinoline (TIQ) and some c omponents of tobacco smoke were investigated for their ability to inhi bit rat brain monoamine oxidase. 1-Cyano-TIQ (1CTIQ), N-(1'-cyanoethyl )-TIQ (CETIQ), N-(1'-cyanopropyl)-TIQ (CPTIQ), and N-(1'-cyanobutyl)-T IQ (CBTIQ) were found to act as competitive inhibitors for both MAO-A and MAO-B. K-i values ranged from 16.4 to 37.6 mu M. N-(Cyanomethyl)-T IQ (CMTIQ) was not found to be an inhibitor (K-i > 100 mu M). These fi ndings may help to explain the in vivo inhibitory effects of tobacco s moke on MAO activity and the suggested protective effect of tobacco sm oking against Parkinson's disease. They also appear to reinforce the u sefulness of reversible MAO inhibitors in smoking cessation and abstin ence. However, different results must be expected between Burley and B right tobacco.