The effect of risperidone on behavioral reactions and gene expression of pro and anti-inflammatory cytokines in neuropathic pain model induced by chronic constriction injury of the sciatic nerve in rat

Abstract

Abstract Background: Neuropathic pain is caused by injury or disease that affects the somatosensory system. Management of patients with chronic neuropathic pain remains a challenge Multiple studies have reported the analgesic effects of serotonin receptor antagonists in different experimental pain models. This study aimed to investigate the effect of systemic administration of risperidone on the behavioral score of neuropathic pain in the chronic contraction (CCI) model in rats. Methods: Inducing neuropathic pain with the CCI model which causes heat hyperalgesia, heat & mechanical allodynia was performed on rats then in 2 phases risperidone effect was determined. in the acute phase, risperidone 1,2,4 mg was administered for 3 groups half an hour before behavioral tests on the 7th,14th, and 21st day after surgery, and in the chronic phase risperidone 1,2,4 mg was administered for 3 different groups from the 1st to 14th days after surgery than on 14th-day behavioral scores were performed. For gene expression analysis, samples are taken from spinal cord tissues in lumbar segments. Results: This study shows chronic administration of risperidone as an antipsychotic drug was effective on heat hyperalgesia & allodynia. However, only the max dosage (4mg) of risperidone showed meaningful improvement in increasing mechanical allodynia. however acute administering of risperidone didn’t show any meaningful changes in behavioral tests on neuropathic pain induced by chronic constriction injury of the sciatic nerve in rats. In addition, gene expression results showed an increase in IL-4 and IL-10 gene expression in the risperidone group compared to the sham group. Conclusion: This study suggests the helpful preventive effects of risperidone in developing and increasing neuropathic pain but it doesn’t have any instant effect.