Summary1. The administration of probenecid to mice increased the concentration of 4-hydroxy-3-methoxyphenylacetic acid (HVA) in the striatum, but did not raise the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC). Some of the HVA is not sensitive to the action of probenecid. This suggests that part of the metabolism of dopamine involves both locations. 6. A group of drugs which are chemically related to amphetamine were tested for their effects on the concentrations of DOPAC and HVA in the striatum. It is suggested that D-amphetamine, 2-aminotetralin and 1,2,3,4-tetrahydroisoquinoline reduced the intraneuronal metabolism of dopamine whereas adamantanamine did not. IntroductionThere are thought to be two locations in the vicinity of the peripheral sympathetic adrenergic nerve ending where noradrenaline can be metabolized. One of these is intraneuronal where oxidative deamination by monoamine oxidase (MAO) takes

Summary A new method for the estimation of 4‐hydroxy‐3‐methoxyphenylethylamine (3‐methoxytyramine) in brain tissue is described. This is based on the formation of a fluorescent derivative by oxidation with potassium ferricyanide in ammonium hydroxide solution. The effects of some drugs on the concentration of 3‐methoxytyramine in the brain are reported. The significance of changes in the striatal concentration of 3‐methoxytyramine is discussed.