Influence of stress on regional brain serotonin metabolism after progesterone treatment and upon plasma progesterone in the rat.

The effect of progesterone upon stress altered serotonin (5-HT) metabolism in various regions of the rat brain was investigated with regard to a possible connection with premenstrual and post-partum depression. When electric footshock was administered to ovariectomized rats pretreated with progesterone or its vehicle, there were generally higher 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) concentrations after progesterone. 5-HT levels were significantly higher in thalamus, hippocampus, raphe, and frontal cortex, 5-HIAA rose significantly in hippocampus, raphe, and frontal cortex. Whereas after electric footshock alone the septum showed highest increases of 5-HT and 5-HIAA and hippocampus ranged last, after pretreatment with progesterone increases of 5-HT and 5-HIAA were least pronounced in septum but rather high in hippocampus. Electric footshock administered to ovariectomized rats also resulted in an increase of plasma progesterone concentration.