Sexually dimorphic responses of rats to fluoxetine in the forced swimming test are unrelated to the function of the serotonin transporter in the brain

Abstract

Due to the prevalence of depression in women, female rats may be a better models for antidepressant research than males. In male rats, fluoxetine inhibited the serotonin (5‐hydroxytryptamine, 5‐HT) transporter (SERT) which is reducing the immobility time in the repeated forced swimming test (rFST). The performance of female rats in this test is unknown. In this study, responses of male and female rats in the rFST under chronic treatment with fluoxetine and the function of SERT in their brains were examined. Wistar rats received oral fluoxetine (females: 0, 1, 2.5, or 5 mg kg‐1 day‐1; males: 0 or 2.5 mg kg‐1 day‐1; in sucrose 10%, 1.5 ml/rat) 1 hr before the test daily for 12 days over the course of the rFST. rFST consisted of a 15 min pretest followed by 5 min sessions of swimming at 1 (test), 7 (retest 1), and 14 (retest 2) days later. SERT functioning was assessed by ex vivo assays of the frontal cortex and hippocampus of rats. Fluoxetine reduced immobility time of males in the rFST while it failed to do so in females. In vitro treatment with fluoxetine inhibited the uptake of 5‐HT of both sexes similarly, while in vivo chronic administration of fluoxetine failed to do so. In summary, rats responded to the chronic treatment with fluoxetine in a sexually dimorphic fashion during the rFST despite the functioning of SERT in their brains remaining equally unchanged. Hence, our data suggest that sexually dimorphic responses to fluoxetine in rFST may be unrelated to the function of SERT in rat brains.

One-capillary lane-maze test in flies: exploratory studies

“…Herein, instead of sucrose intake, the behavioural scores in the capillary zone filled with sucrose were used to calculate a 'preference index' as a proxy for sucrose preference in the lane-maze. In addition, the preference index based on behavioural scores would also permit a behavioural test shorter than 24 h, which is habitual in neuroscience 24,27,28,29 .…”

Lane-maze for preference testing in flies

“…11,12 In laboratory rodents, symptoms of stress may be assessed using several behavioural tests such as positive or negative avoidance, forced swimming, tail suspension, sucrose preference and others. 13,14,15,16, 17…”

“…In the field of psychopharmacology, behavioural tests in rodents like forced swimming, tail suspension, and others are habitually short (5 to 15 minutes). 13,14,15,16,17 Therefore, here, a short version of a lane-maze test (5 minutes) was tried. To validate the 5-min lane-maze test, adult, virgin, male and female flies undergone 0, 2, 8 or 20 h of food deprivation before behavioural testing.…”

“…11,12 In laboratory rodents, symptoms of stress may be assessed using several behavioural tests such as positive or negative avoidance, forced swimming, tail suspension, sucrose preference and others. 13,14,15,16,17 Since the pioneer study reporting learned helplessness in flies, 18 several attempts to develop models and behavioural tests for stress response in Drosophila have been made. 19,20 Flies trained to receive inescapable heat shocks failed to escape from the stressor even when the opportunity appeared, different from those trained with escapable heat shocks.…”