An Investigation of the Role of Sex Difference in the Effect of Fluoxetine on Behavioral and Biochemical Changes in Male and Female Rats Exposed to Stress

Unpredictable stressors cause changes in behavioral parameters such as motor and exploratory behaviors, feeding, and sexual and anxiety behaviors. Stress leads to the release of corticosteroids and, as a result, causes dysfunction in different parts of the nervous system. A decrease in the synaptic levels of serotonin or norepinephrine in different parts of the brain such as the prefrontal cortex and a decrease in BDNF production in the hippocampus may also contribute to stress-related complications. Posttraumatic stress disorder occurs in some people after facing a severe stressful event. In PTSD, the activity and function of many physiological systems are disturbed. Fluoxetine, or Prozac, is used to treat neurological disorders such as depression and anxiety and inhibits the reuptake of serotonin by the serotonin transporter (SERT) in neurons. Some studies have shown that females respond better to SSRI antidepressants than males, which may be due to the interaction between estrogenic and serotonergic pathways. BDNF is a member of the neurotrophin family and is expressed in several tissues and cells such as the brain and blood. Its role in several mental disorders, such as depression, anxiety, eating disorders, and PTSD, has been identified. SPS (single prolonged stress) as an animal model of PTSD decreases the mRNA expression of BDNF in hippocampus rats and causes anxiety-like behaviors. The role of gender differences in the effect of antidepressants and clinical interventions in psychotic diseases is also discussed. Sex hormones in women affect the pharmacokinetics and efficacy of antidepressants. Women respond better to fluoxetine than men during reproductive years. Considering the different results regarding the effectiveness of effective drugs in the treatment of psychotic diseases in both sexes, in this study, we aim to investigate the response of male and female rats exposed to stress to the trial of fluoxetine.

In this experimental study, Wistar male and female rats with an average weight of 200-250 grams were used (56 animals, 8 groups of 7). The selection of the number of animals was based on previous studies in this field. After the drug intervention period, and fear and anxiety suppression test, the animals were killed under deep anesthesia, and a blood sample was collected to prepare serum to measure BDNF and corticosterone levels (using the Eliza kit of Germany Zelbio Company and according to the kit protocol). All experiments were performed according to the laboratory animal protocol of Mazandaran University of Medical Sciences.The work steps are as follows: 1. Creation of PTSD through SPS was done in three stages, 2. Drug intervention: the drug dose for all groups is 10 mg/kg/day for 4 weeks dissolved in drinking water, 3. Evaluation of anxiety-like behaviors with the light-dark box (L/D BOX), 4. Evaluation of the ability to forget painful memories with the fear silence test, 5. Measurement of BDNF and corticosterone in serum by Eliza method.

In this study, it was observed that male and female rats that were exposed to single prolonged stress showed a decrease in fear extinction an increase in anxiety-like behaviors in the dark-light box test, and an increase in serum corticosterone. Fluoxetine led to an increase in the percentage of fear extinction, a decrease in the Entrance Latency in the light area, the Time in the Light Compartment, the number of rearing, and a decrease in serum corticosterone significantly in both sexes(P<0.05). The change in serum BDNF levels in both sexes before and after stress was not significant.

The results of the study showed that exposure to stress leads to behavioral and biochemical damage in male and female rats. The use of fluoxetine 10 mg/kg for 4 weeks improved the damage caused by stress, but there was a significant difference in Response of both genders to the above treatment was not observed.