Differences in regional brain catecholamine metabolism after a decrease in blood pressure

Using a sensitive radiometric assay for determination of catecholamines, the α-methyl-para-tyrosine-induced catecholamine disappearance was studied in discrete brain regions of rats after acute hypotension. The decrease in blood pressure was induced either by controlled haemorrhage or by the administration of guanethidine. In both cases an increase of the α-methyl-para-tyrosine-induced noradrenaline disappearance was observed in the nucleus commissuralis and the A₁-region in the medulla oblongata. In the paraventricular nucleus the disappearance of noradrenaline as well as that of adrenaline was enhanced. The results are in support for the involvement of catecholamines in particular brain regions in the regulation of blood pressure.