Pharmacological properties of tetrahydropapaveroline and their relation to the catecholamines

Peyote, a potential ethnopharmacologic agent for alcoholism and other drug dependencies: possible biochemical rationale

The authors examine folk psychiatry among Native American Church members from an enthnopharmacologic viewpoint. Alcohol and opiate abuse among Indian and non-Indian are presented in case histories proving to be asymptomatic under Indian guidance and through participation in the peyote ritual. The biochemical alkaloids common in the peyote cactus, rather than just the psychoactive substances (mescaline), are purported to be pharmacologically similar to the neuroamine-derived alkaloids found in the brain during alcohol intoxification. Evidence is reviewed that points out possible common features of alcohol and opiate dependence leading to the speculation for a common mode of treatment may reside in plants rich in isoquinoline alkaloids.

Disposition of catecholamine-derived alkaloids in mammalian systems

Tetrahydropapaveroline, the tetrahydroisoquinoline alkaloid derived from dopamine, is converted in vivo by rats and by rat liver and brain preparations to tetrahydroprotoberberine alkaloids. The latter alkaloids have also been identified for the first time in the urine of parkinsonian patients receiving L-dopa therapy. These findings suggest that man, like plants, may have the ability to elaborate several classes of alkaloids with potentially important pharmacological consequences. Thus, this newly demonstrated ability of mammalian systems to evoke the biosynthesis of benzyl-tetrahydroisoquinoline-derived alkaloids - a capability previously considered unique to plants - elects the tetrahydroprotoberberine alkaloids as representative of the first class of a possible constellation of complex mammalian alkaloids elaborated from the neuroamines.

Pharmacological properties of tetrahydropapaveroline

Tetrahydropapaveroline (thp) exerts β-sympathomimetic effects similar to those of isoprenaline. On guinea-pig isolated atria, thp elicits positive inotropic and chronotropic activities which are not abolished by previous reserpinization of the animals; on isolated mammalian heart these effects are associated with an increase in coronary flow. In the dog, thp increases myocardial contractile force and rate, elicits a hypotensive effect and stimulates respiratory activity in normal and reserpinized animals; when injected intra-arterially the drug causes vasodilatation. All the effects are prevented by the β-adrenergic blocking agents propranolol, dichloroisoprenaline and pronethalol. Structure-activity relationships between tetrahydroisoquinoline derivatives and their open-ring phenylethylamine congeners, which are closely related to sympathomimetic drugs, are discussed.