protection against blood-brain barrier permeability as a possible mechanism for protective effects of thymoquinone against sickness behaviors induced by lipopolysaccharide in rats

Background: blood-brain barrier (bbb), as well-known protection for the brain, plays an active role in normal homeostasis. it might be changed by a range of inflammatory mediators to have a role in sickness behaviors. objectives: regarding the anti-inflammatory effects of thymoquinone (tq), its protection against bbb permeability, as a possible mechanism for protective effects against sickness behaviors elicited by lipopolysaccharide (lps), was evaluated in rats. methods: the animals were grouped as follows and treated (n = 10 in each): (1) control (saline); (2) lps 1 mg/kg, was injected two hours before behavioral tests for two weeks; (3-5) 2, 5, and 10 mg/kg tq, respectively was injected 30 min before lps injection. open-field (of), elevated plus-maze (epm) and forced swimming test (fst) were done. finally, the animals were anesthetized to evaluate for bbb permeability using evans blue (eb) dye method. results: compared with control, lps decreased the peripheral distance and crossing and also total crossing and distance in of, (p < 0.01 - p < 0.001). the central crossing and distance and central time in all three treatment groups were more than lps (p < 0.05 - p < 0.001). lps also reduced the entries and the time spent in the open arm while increased the time spent in the closed arm in epm (p < 0.05 - p < 0.001). the effects of lps were reversed by tq (p < 0.05 - p < 0.001). in fst, the immobility time and active time were increased and decreased by lps compared with control (p < 0.001), respectively. in all three tq-treated groups, the active and climbing times were more while the immobility time was fewer than the lps (p < 0.05 - p < 0.001). the animals of the lps group showed more eb dye content in their brain tissue than the control group (p < 0.05 - p < 0.001). tq significantly reduced eb dye content of the brain tissues (p < 0.05 - p < 0.001). conclusions: according to this study, protection against bbb permeability as a possible mechanism for the protective effects of tq against sickness behaviors induced by lps might be suggested.