The effect of tranquillizing drugs on the concentration of the sulphate ester of 4-hydroxy-3-methoxyphenylethane-1,2-diol in rat brain.

A total of 17 butyrophenone, phenothiazine, benzodiazepine and imidazoline tranquillizing drugs were examined for their ability to increase the cerebral concentration of the sulphate ester of 1(4-hydroxy-3-methoxyphenyl)ethane-1,2-diol (MHPG-SO(3) H), a metabolite of noradrenaline in the rat brain. Of these drugs, when given in a dose of 10 mg/kg i.p., only trifluperidol, haloanisone, azaperone, clozapine and haloperidol were found to increase the cerebral concentration of MHPG-SO(3) H. This effect is unrelated to the ability of such drugs to antagonize the lethal effects of an intravenous injection of noradrenaline and suggests that the properties of the central noradrenaline receptors differ from those of the peripheral noradrenaline receptors.