Gender differences in rat brain serotonin transporter levels after exposure to prenatal stress and/or chronic mild stress in early adulthood

Abstract

Prenatal stress and chronic mild stress are great risk factors for developing mood disorders. When the stress response cannot cope with the amount of stress, the brain will undergo longterm changes. These changes can lead to several diseases associated with chronic stress. In these diseases the serotonergic system is a main player, especially in mood disorders. Serotonin is taken up by the serotonin transporter, which is presynaptically localized. In case of depression, serotonin levels are to low. Most commercial anti-depressants act by inhibiting the reuptake of serotonin, thus increasing serotonin levels again. In this investigation we focused on the serotonin transporter in rats which received prenatal stress and/or chronic mild stress in early adulthood. Earlier behavioural investigations with these animals revealed that depression-like behavior was increased after prenatal and/or chronic mild stress. Our goal is to link behavioural changes with the possible changes is serotonin transporter in the brain. We used immunohistochemistry to quantify the amount of serotonin transporter in the dorsal hippocampus, more specifically in the projection regions of the CA3 and dentate gyrus. In both brain regions we observed a significant increase in the amount of serotonin transporter in male rats which had been chronically stressed, compared with the control rats. Prenatal stress itself was not effective but it appeared to reduce the effect of chronic stress. The females had no significant differences between groups, but with one exception, in the outer DG, i.e. the group which received both prenatal stress and chronic mild stress had significant more serotonin transporters when compared with the group which received only prenatal stress.