Changes in nociceptive sensitivity in female rats with experimental temporomandibular joint arthritis under immunomodulation

Objective. To investigate changes in pain sensitivity in female rats with experimental temporomandibular joint arthritis under immunomodulation. Material and methods. The study was conducted on 51 female rats. Six experimental groups were formed: group 1 — intact animals; group 2 — administration of Imunofanum on days 2, 4, 6, 8, and 10; group 3 — injection of sodium monoiodoacetate into temporomandibular joint (TMJ) on day 1; group 4 — injection of sodium monoiodoacetate into TMJ on day 1 followed by Imunofanum administration on days 2, 4, 6, 8, and 10; group 5 — injection of sodium monoiodoacetate into TMJ on day 1 followed by Imunofanum administration on days 14, 16, 18, 20, and 22. Pain response threshold was assessed by measuring the tail withdrawal latency in response to light-thermal stimulation (tail-flick test). Measurements were performed in diestrus phase of estrous cycle (microscopic examination of vaginal smears). Results. Reduction of tail-flick latency typical for animals that received sodium monoiodoacetate into TMJ did not occur under immunomodulation. This effect of Imunofanum was independent of timing of drug administration. Conclusion. Administration of Imunofanum to female rats at early stages of temporomandibular joint arthritis induced by intra-articular sodium monoiodoacetate injection prevents enhancement of nociceptive sensitivity. Delayed administration of this drug leads to higher pain response threshold in animals with experimental temporomandibular joint arthritis.