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Recent investigations have focused on the mitochondrion as a direct drug target in the treatment of metabolic diseases (obesity, metabolic syndrome). Relatively few studies, however, have explicitly investigated whether drug therapies aimed at changing behavior by altering central nervous system (CNS) function affect mitochondrial bioenergetics, and none has explored their effect during early neonatal development. The present study was designed to evaluate the effects of chronic treatment of newborn male rats with the selective serotonin reuptake inhibitor fluoxetine on the mitochondrial bioenergetics of the hypothalamus and skeletal muscle during the critical nursing period of development. Male Wistar rat pups received either fluoxetine (Fx group) or vehicle solution (Ct group) from the day of birth until 21 days of age. At 60 days of age, mitochondrial bioenergetics were evaluated. The Fx group showed increased oxygen consumption in several different respiratory states and reduced production of reactive oxygen species, but there was no change in mitochondrial permeability transition pore opening or oxidative stress in either the hypothalamus or skeletal muscle. We observed an increase in glutathione S-transferase activity only in the hypothalamus of the Fx group. Taken together, our results suggest that chronic exposure to fluoxetine during the nursing phase of early rat development results in a positive modulation of mitochondrial respiration in the hypothalamus and skeletal muscle that persists into adulthood. Such long-lasting alterations in mitochondrial activity in the CNS, especially in areas regulating appetite, may contribute to permanent changes in energy balance in treated animals.

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Protein restriction during prenatal, postnatal, or in both periods has a close relationship with subsequent development of cardiovascular disease in adulthood. Elevated brain levels of serotonin and its metabolites have been found in malnourished states. The aim in the present study was to investigate whether treatment with fluoxetine (Fx), a selective serotonin reuptake inhibitor, mimics the detrimental effect of low-protein diet during the perinatal period on the male rat heart. Our hypothesis is that increased circulating serotonin as a result of pharmacologic treatment with Fx leads to cardiac dysfunction similar to that observed in protein-restricted rats. Male Wistar rat pups received daily subcutaneous injection of Fx or vehicle from postnatal day 1 to postnatal day 21. Male rats were euthanized at 60 days of age and the following parameters were evaluated in the cardiac tissue: mitochondrial respiratory capacity, respiratory control ratio, reactive oxygen species (ROS) production, mitochondrial membrane potential, and biomarkers of oxidative stress and antioxidant defense. We found that Fx treatment increased mitochondrial respiratory capacity (123%) and membrane potential (212%) and decreased ROS production (55%). In addition we observed an increase in the antioxidant capacity (elevation in catalase activity (5-fold) and glutathione peroxidase (4.6-fold)). Taken together, our results suggest that Fx treatment in the developmental period positively affects the mitochondrial bioenergetics and antioxidant defense in the cardiac tissue.

The serotonin reuptake is mainly regulated by the serotonin transporters (SERTs), which are abundantly found in the raphe nuclei, located in the brainstem. Previous studies have shown that dysfunction in the SERT has been associated with several disorders, including depression and cardiovascular diseases. In this manuscript, we aimed to investigate how gender and the treatment with a serotonin selective reuptake inhibitor (SSRI) could affect mitochondrial bioenergetics and oxidative stress in the brainstem of male and female rats. Fluoxetine, our chosen SSRI, was used during the neonatal period (i.e., from postnatal Day 1 to postnatal Day 21-PND1 to PND21) in both male and female animals. Thereafter, experiments were conducted in adult rats (60 days old). Our results demonstrate that, during lactation, fluoxetine treatment modulates the mitochondrial bioenergetics in a sex-dependent manner, such as improving male mitochondrial function and female antioxidant capacity.