The effects of Nigella sativa on sickness behavior induced by lipopolysaccharide in male Wistar rats

Objective: Neuroimmune factors contribute on the pathogenesis of sickness behaviors. Nigella sativa (NS) has anti-inflammatory, anti-anxiety and anti-depressive effects. In the present study, the effect of NS hydro-alcoholic extract on sickness behavior induced by lipopolysaccharide (LPS) was investigated. Materials and Methods: The rats were divided into five groups (n= 10 in each): (1) control (saline), (2) LPS (1 mg/kg, administered two hours before behavioral tests), (3-5) LPS-Nigella sativa 100, 200 and 400 mg/kg (LPS-NS 100, LPS-NS 200 and LPS-NS 400, respectively). Open-field (OF), elevated plus maze (EPM) and forced swimming test (FST) were performed. Results: In OF, LPS reduced the peripheral crossing, peripheral distance, total crossing and total distance compared to control (p< 0.01-p< 0.001). The central crossing, central distance and central time in LPS-NS 100, LPS-NS200 and LPS-NS 400 groups were higher than LPS (p< 0.01-p< 0.001). In EPM, LPS decreased the open arm entries, open arm time and closed arm entries while increased the closed time compared to control (p< 0.001). Pretreatment by NS extract reversed the effects of LPS (p< 0.05-p< 0.001). In FST, LPS increased the immobility time while, decreased the climbing and active times compared to control (p< 0.05-p< 0.001). In LPS-NS 100, LPS-NS 200 and LPS-NS 400 groups the immobility time was less while, the active and climbing times were more than those of LPS (p< 0.05-p< 0.001). Conclusion: The results of the present study showed that the hydro-alcoholic extract of NS reduced the LPS-induced sickness behaviors in rats. Further investigations are required for better understanding the responsible compound (s) and the underlying mechanism(s).