Effect of Probiotic Administration on Acute Inflammatory Pain

Acute inflammatory pain causes by direct stimulation of nociceptors and release of inflammatory mediators and cytokines. Probiotics are capable to modulate the immune system, down regulate the inflammatory mediators, and increase regulatory and anti-inflammatory cytokines. The aim of this study was to examine the effect of oral administration of probiotics on behavioral, cellular and molecular aspects of acute inflammatory pain in male rats. Adult male Wistar rats (200 - 220 g) were selected and randomly divided into 7 experimental groups (CFA, CFA control, CFA + vehicle (distilled water), CFA + 3 doses of probiotics, CFA + indomethacin) and each group was divided into 3 subgroups based on different time points (days 0, 3, and 7) (n = 6 rats, each group). Complete Freund’s adjuvant (CFA)-induced arthritis (AA) was caused by a single subcutaneous injection of CFA into the rats’ left hind paw on day 0. Different doses of probiotics (1/250, 1/500 and 1/1000 (109 CFU/g)) was administered daily (gavage) after the CFA injection. Blood samples were taken from the vessel retro-orbital corners of rat’s eyes. After behavioral and inflammatory tests, the lumbar segments of rat’s spinal cord (L1 - L5) were removed. Hyperalgesia, edema, serum TNF-α and IL-1β levels and NF-κB expression were assessed on days 0, 3, and 7 of the study. The results of this study showed the role of effective dose of probiotics (1/500) in reducing edema (P = 0.0009), hyperalgesia (P = 0.0002), serum levels of TNF-α (P = 0.0004) and IL-1β (P = 0.0004) and NF-κB expression (P = 0.0007) during the acute phase of inflammatory pain caused by CFA. It seems that an effective dose of probiotics due to its direct effects on inhibition of intracellular signaling pathways and pro-inflammatory cytokines can alleviate inflammatory symptoms and pain in the acute phase.