Independence of diurnal rhythms of plasma corticosterone and hypothalamic serotonin content.

Diurnal changes in plasma corticosterone an hypothalamic serotonin content have been investigated in normal male rats and in animals, in which anterior connections of the medial basal hypothalamus were interrupted. While in normal animals there is an inverse time-relationship between the rhythmicity of plasma corticosterone and hypothalamic serotonin content, frontal isolation of the medial basal hypothalamus eliminates only the plasma corticosterone rhythm without affecting hypothalamic serotonin content rhythm. It seems probable that hypothalamic serotoninergic terminals do not participate in the regulation of diurnal secretion of adrenocorticotroph hormone.