Bromelain reduced pro-inflammatory mediators as a common pathway that mediate antinociceptive and anti-anxiety effects in sciatic nerve ligated Wistar rats.

The involvement of pro-inflammatory mediators complicates the complex mechanism in neuropathic pain (NP). This study investigated the roles of bromelain against pro-inflammatory mediators as a mechanism that underpins its antinociceptive and anti-anxiety effects in the peripheral model of NP. Sixty-four male Wistar rats randomly divided into eight groups, were used for the study. A chronic constriction injury model of peripheral neuropathy was used to induce NP. Tail-immersion and von Frey filaments tests were used to assess hyperalgesia while open field and elevated plus mazes were used to assess anxiety-like behaviour. NF-кB, iNOS, nitrate, and pro-inflammatory cytokines were investigated in the plasma, sciatic nerve, and brain tissues using ELISA, spectrophotometer, and immunohistochemistry techniques after twenty-one days of treatment. Bromelain significantly (p < 0.05) improved the cardinal signs of NP and inhibited anxiety-like behaviours in ligated Wistar rats. It mitigated the increases in cerebral cortex interleukin (IL) -1ß, IL-6, and PGE2 levels. Bromelain reduced NF-кB, IL-1ß, IL-6, TNF-α, PGE2, and nitrate concentrations as well as the expression of iNOS in the sciatic nerve. Hence, the antinociceptive and anxiolytic effects of bromelain in the sciatic nerve ligation model of NP is in part due to its ability to reduce nitrosative and inflammatory activities.

Analgesic properties of aqueous bark extract of Adansonia digitata in Wistar rats.

The study investigated the analgesic effect of the aqueous extract of the bark of Adansonia digitata using Wistar rats. Thirty Wistar rats weighing between 150 and 170g of either sex were used for the study. Animal were picked randomly and grouped into six with each group made up of five animals (3 females and 2 males). Oral administration of 10ml/kg of normal saline were given to control group; 5mg/kg of indomethacin to reference group; and 25mg/kg, 50mg/kg, 100mg/kg or 200mg/kg of aqueous extracts of Adansonia digitata to each of the test groups respectively.Hotplate and formalin paw-licking tests were used for nociceptive assessment. Animals treated with aqueous bark extract of Adansonia digitata showed significantly (p<0.05) prolonged response time to thermal stimuli (4.42±0.11s) compared with control group (3.29±0.29s) in a dose dependent manner. Results formalin paw-licking test showed that at early phase, animals administered with aqueous bark extract of Adansonia digitata significantly (p<0.05) have reduced paw-licking time (47.88±3.48-40.80±3.85s) compared with the control group (91.51±7.32s). In the late phase, aqueous bark extract of Adansoni adigitata significantly (p<0.05) reduced the paw-licking time (43.57±2.6-25.49±3.46s) compared with the control group (66.31±5.04s). It is hereby concluded that aqueous bark extract of A. digitata possesses a strong analgesic effect.