Effective action of silymarin against ketamine-induced schizophrenia in male mice: Insight into the biochemical and molecular mechanisms of action

Background

Neurochemical dysregulations resulting from N-methyl-D-aspartate hypofunction (NMDA), are exacerbated by neuroimmune and oxidative stress and are known risk factors for neuropsychiatric disorders like schizophrenia-like diseases. Here, we investigate the protective and curative effects, and mechanisms of silymarin, a polyphenolic flavonoid with neuroprotective functions in preventive-reversal model of ketamine, an NMDA antagonist in mice.

Methods

Mice were grouped into 6 cohorts (n = 9). In the pre-treatment, groups 1 and 2 received saline (10 mL/kg/p.o.), groups 3 and 4 (silymarin, 50 and 100 mg/kg/p.o.), and group 5 (risperidone, 0.5 mg/kg/p.o.) consecutively for 14 days, then combined with ketamine (20 mg/kg/i.p.) injection in groups 2–5 from days 8–14. However, mice in reversal study received intraperitoneal injection of ketamine for 14 days before silymarin (50 and 100 mg/kg, p.o) and risperidone (0.5 mg/kg, p.o.) treatment between days 8–14. The consequences on schizophrenia-like behavior, neurochemistry, inflammation, and oxidative/nitrergic stress markers were evaluated in critical brain regions of the disease.

Results

Silymarin prevented and reversed ketamine-induced increase in dopamine, 5-hydroxyltryptamine, acetylcholinesterase, malondialdehyde and nitrite levels in the striatum, prefrontal-cortex and hippocampus. These were accompanied by improvement in hyperlocomotion, stereotypy, memory, and social impairments, notably devoid of cataleptogenic potential. Complementarily, silymarin reduced myeloperoxidase, tumor-necrosis factor-α, and interleukin-6 concentrations relative to the ketamine group. Moreover, ketamine-induced decreased brain-derived neurotrophic factor, glutathione, catalase, superoxide-dismutase levels were normalized by silymarin in the brain regions relative to ketamine.

Conclusions

Overall, these findings suggest that silymarin's antipsychotic effect might be primarily associated, among other mechanisms, with the normalization of neurochemical and neurotrophic changes in the mice brains.