American Journal of Research Communication www.usa-journals.com Thabet, et al., 2016: Vol 4(2) 1 Investigation of analgesic effect of PDE-4 inhibitors on adjuvant-induced pain in a rat model of rheumatoid arthritis Romany Helmy Thabet 1 , Maher Salamah Raja Alanazi 2 , Ibrahim Abdulhakim Alduraywish 2 , Abdulaziz Saud Saad Alhuwaymil 2 , Hanadi Awad Salman Alanazi 2 1 Pharmacology department, faculty of medicine, Northern Border University, Arar, Saudi Arabia 2 Medical Student, faculty of medicine, Northern Border University, Arar, Saudi Arabia Abstract Background and aim of the work: Rheumatoid arthritis (RA) is an autoimmune disorder of unknown cause. It is a highly inflammatory polyarthritis disease often leading to joint destruction, deformity and loss of function. There is conflicting data about the effect of PDEIs on pathogenesis of RA. This work aims at investigation of the potential analgesic effect of rolipram as representative of PDEIs on adjuvant-induced pain in a model of RA in rats that exhibit several pathological changes similar to those occurring in RA. Methods: In the present study, we used rat model of adjuvant-induced arthrits (AIA), a model of RA in rats that exhibit several pathological changes similar to those occurring in RA in human, by subplantar administration of Freund’s adjuvant into hind paws of rats. Pain threshold to pressure on hind paws was measured daily from day 0 until day 30 after adjuvant inoculation. Results: Rolipram therapy, either prophylactic or therapeutic, significantly leads to marked suppression of adjuvant arthritis in rats depending on the dose administered. Hyperalgesia of adjuvant arthritic rats was significantly reduced in rolipram-treated animals compared to non- treated group. Interestingly, the present work demonstrated that hyperalgesia was significantly attenuated by DMSO treatment. Conclusion: The results presented in this study show that rolipram, a PDE 4 inhibitor displayed anti-hyperalgesic actions in adjuvant arthritic rats in a dose-dependant manner. Further studies are needed to prove analgesic efficacy of rolipram to exclude effect of the solvent DMSO exhibited in this study.