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The metabolism of a number of biogenic amines has been simulated by using data obtained from studies of the individual enzymes from pig brain. It is shown that beta-hydroxylated amines such as noradrenaline and octopamine are metabolized primarily to the alcoholic metabolite whereas amines lacking this group [e.g. dopamine (3,4-dihydroxyphenethylamine) and 5-hydroxytryptamine] are metabolized at low concentrations to give the corresponding acid. Increase in the amine concentration results in an increase in the proportion of the alcoholic metabolite formed and this may in part account for the effects of the drug reserpine on amine metabolism. The effects of disulfiram (Antabuse) and ethanol (acting through its metabolite acetaldehyde) on amine metabolism may be understood in terms of this simulated model. It is shown that drugs that affect this system also cause alterations in the steady-state concentrations of the intermediate aldehydes and the possible implications of this are discussed.

After chronic administration of ethanol to mice by the intragastric route head twitches occur as part of the ethanol withdrawal syndrome. Treatments which reduce brain 5-hydroxytryptamine or increase brain noradrenaline inhibited ethanol withdrawal head twitches, whereas treatments which increase brain 5-hydroxytryptamine or reduce brain noradrenaline were capable of inducing head twitches in control animals.