The effects of gonadectomy on monoamine metabolism in three regions of mouse brain

The concentrations 5-hydroxytryptamine, noradrenaline, their precursors and metabolites have been determined in three regions of mouse brain following gonadectomy; the rates of depletion of 5-hydroxytryptamine and noradrenaline following synthesis blockade have also been examined. Previous investigations have shown that gonadectomy results in changes in hypothalamic catecholamine metabolism; this report shows that changes are not confined to the hypothalamic area and suggests that the effects in other areas of the brain may contribute to the increased incidence of mental disturbances in man when hormone levels are drastically altered. Gonadectomy results in reduced 5-hydroxytryptamine and 5-hydroxyindoleacetic acid concentrations in all regions of the mouse brain. Normetanephrine concentrations are significantly increased and the rate of depletion of noradrenaline from the brain following synthesis blockade is markedly accelerated following gonadectomy; this suggests that circulating steroid sex hormones may exert a stabilising effect on brain catecholamine stores.