Neuropharmacological Effects of Paeoniflorin in Traumatic Brain Injury Mouse Model

Abstract

Traumatic brain injury (TBI) is a serious condition that can lead to immense complexities. Post injury complications vary according to the severity of the injury. In this study aftermaths of TBI were studied by subjecting the mice to injury. BALB/c male mice approximately of 3-4 months of age were utilized in the study. Paeoniflorin (PF) was tested for its neuroprotective effects, ibuprofen was used as a positive control and weight drop model of TBI was used to induce an injury. Diffuse brain injury was induced by allowing a metal rod of 100g to drop from a height of 4 cm in a free fall directly on the exposed crania for 3 times. Mice were randomly divided into sham-operated, TBI 100 g weight drop, TBI with ibuprofen (30 mg/kg/day), TBI with PF (5 mg/kg/day) and TBI with PF (40mg/kg/day) treatment groups. Neurological Severity Score (NSS) was performed at 24, 96 and 264 h of TBI. Sham group showed the lowest score at 24 h whereas TBI group showed the highest score followed by ibuprofen, PF 5 mg and PF 40 mg groups. At 96 h PF 5 mg group showed more improvement compared to PF 40 mg group. By 264 h no significant difference was observed among the groups. In open field test no significant difference was found among the groups in locomotor activity. Sham and PF 5 mg groups spent significantly more time in the center of the arena compared to TBI group (sham= p<0.01, PF 5 mg= p<0.05) demonstrating low anxiety levels. For first 5 min lowest rearing number was observed in TBI group. Significant difference was found between TBI group and all other groups. In the last 5 min, TBI group showed no adaptability as the number of rearings was the same in the initial 5 min and last five min. In grooming analysis all the groups showed very negligible relaxed grooming and no

XII significant difference was found among the groups in the initial 5 min. However in the last 5 min all the groups exhibited considerable total of relaxed grooming except for TBI group. TBI group showed the highest anxious grooming compared to all group in the initial 5 min. During the last 5 min sham, PF 5 mg and PF 40 mg groups showed almost negligible anxious grooming, while the TBI mice were unable to adapt to the new environment and showed the highest anxious grooming. Both tail suspension and forced swim test displayed promising results; both doses of PF showed no signs of depression and stress, and exhibited results similar to sham group. In fear conditioning, all groups showed acquisition of memory, but no significant difference was found among the groups. Similarly no significant difference was found among the groups in fear context test. In edema percentage analysis at 48 h significant difference was found between ibuprofen and sham, TBI, PF 5 mg, PF 40 mg group (p<0.01). However at 264 h no significant difference was found among the groups. Acetylcholine analysis in amygdala showed lowest acetylcholine concentration in TBI group at 48 h of the study protocol. Significant difference was found between TBI and sham (p<0.05), PF 40 mg groups (p<0.001). Ibuprofen and PF 5 mg showed concentrations close to TBI concentrations. At 264 h PF 5 mg group showed the lowest acetylcholine levels. TBI group showed similar results compared to PF 5 mg group. Significant difference was found between TBI and sham (p<0.001), ibuprofen (p<0.01), PF 40 mg (p<0.001). These results conclude that PF 5 mg performed better in most tests however in amygdala PF 40 mg showed better results. Weight drop method is an effective injury model and results in neurological deficits common in patients of TBI such as depression, anxiety, and cognitive, sensory and motor impairment.