Prenatal methotrexate injection increases behaviors possibly associated with depression and/or autism in rat offspring; A new animal model for mental disorder, based on folate metabolism deficit during pregnancy

Abstract

Background: Deficiency of folate, an essential vitamin for DNA synthesis and methylation, is reported as a risk factor for mental disorders. Considering a possibility that folate metabolism deficit during pregnancy may disturb CNS development and increase mental disorders in offspring, we treated pregnant rats with methotrexate (MTX), an inhibitor of folate metabolic enzyme, and evaluated offspring behaviors. Methods: Saline or MTX was intraperitoneally administered to female SD rats on gestational day 17. Offspring behaviors were evaluated during approximately 6-9 weeks old; prepulse inhibition (PPI), social interaction (SI), locomotor activity (LA), and forced swimming test (FST) for evaluation of schizophrenia, depression, and autism related behaviors; the elevated plus maze (EPM) and the light-dark box (LD) test for evaluation of anxiety. Results: Compared to saline-treated group, MTX-treated group showed decrease of SI and increase of immobility time in FST. In addition, increases of time spent in the light box and shuttling between the light-dark boxes were observed in LD test. On the other hand, no changes were confirmed in EPM, LA, and PPI. Conclusion: Decrease of SI and increase of immobility time in FST may suggest association of this animal model with depression and/or autism. Increase of time spent in the light box and shuttling between the light-dark boxes may indicate changes in anxiety or cognitive level to environment, or repetitive behaviors in autism. Although further studies are warranted to characterize this animal model, at least we can say that prenatal MTX exposure, possibly causing folate metabolism deficit, affects offspring behaviors.

Synergistic anti‐depressive effect of combination treatment of Brexpiprazole and selective serotonin reuptake inhibitors on forced swimming test in mice

“…Animals were assigned to four groups (Table 1). FST was conducted according to previous reports with slight modification 9,11,12 . After the administration of brexpiprazole and either of SSRIs, each mouse was placed into an acrylic cylinder (25 cm high × 9 cm inner diameter) filled with water (23 ± 1°C) up to 10 cm from the bottom of cylinder for 6 min.…”

“…FST was conducted according to previous reports with slight modification. 9,11,12 After the administration of brexpiprazole and either of SSRIs, each mouse was placed into an acrylic cylinder (25 cm high × 9 cm inner diameter) filled with water (23 ± 1°C) up to 10 cm from the bottom of cylinder for 6 min. Then, the mobility time of the mouse was measured using SCANET (Melquest Co., Ltd., Toyama, Japan), and the immobility time was determined during last 4 min.…”

“…Forced swimming test (FST) is used to evaluate depression-like behavior and antidepressant efficacy in rodents, in which immobility is thought to reflect behavioral despair in rodents. 9,10 In order to demonstrate synergistic antidepressant-like effect in animals, we evaluated combination effect of brexpiprazole with SSRIs, using each ineffective dose based on unpublished in-house data, on immobility time in FST in mice. For this combinatory study, we selected SSRIs (escitalopram, fluoxetine, paroxetine, and sertraline) already approved for treatment of MDD.…”