doi:10.1016/j.ejpain.2007.03.387 373 NEUROPATHIC PAIN IS DECREASED IN A2A ADENOSINE RECEPTOR KNOCKOUT MICE S.A. Bura * ,a , X. Nadal a , C. Ledent b , R. Maldonado a , O. Valverde a a Laboratori De Neuropharmacologia, Departament De Ciencies Experimentals I De La Salut, Universitat Pompeu Fabra, Barcelona, Spain b IRIBHM, Universite Libre De Bruxelles, Belgium Background and aims. We have evaluated the possi- ble involvement of A2A adenosine receptor in the development and expression of neuropathic pain. Methods For this purpose, partial ligation of the sci- atic nerve was performed in A2A knockout mice and wild-type littermates. The development of mechanical and thermal allodynia, as well as thermal hyperalgesia was evaluated by using the von Frey fil- ament model, the cold-plate test and the plantar test, respectively. Results. In wild-type mice, sciatic nerve injury led to a neuropathic pain syndrome revealed in these nociceptive behavioural models. A significant decrease of the mechanical allodynia and a suppression of both thermal hyperalgesia and allodynia were observed in A2A recep- tor deficient mice. Conclusions. These results reveal the involvement of A2A in the control of neuropathic pain and suggest a new potential therapeutic use of A2A antagonists. doi:10.1016/j.ejpain.2007.03.388 374 SPINAL CORD CHANGES IN RATS AFTER IMMOBILISATION S.H. Butler *, M.S. Butler, H. Sharma, T. Gordh Department of Anesthiology and Intensive Care, Aca- demic Hospital of Uppsala, Sweden Aim of investigation. Abnormal central sensory pro- cessing is considered a part of CRPS. Central changes have been shown in animals and man after immobilisa- tion and may be linked to CRPS. This study looked at c- fos, c-jun induction and microglial activation in rats after immobilsation. Methods. Sprague–Dawley rats, 200–250 g were used. Five + five control rats were followed. Ten + ten rats had fibreglass casts immobilising the left upper limb for 2 weeks. Following cast removal, study and control rats were perfused with formalin, the cervical spinal cords removed and stored in sucrose at À70 °C. Immu- nostaining for c-fos, c-jun and microglial activity were done on serial slices from the cervical enlargement. Slides were reviewed by a blinded reviewer for fos induc- tion and microglial activation. Results. Unilateral increases in c-fos, less with c-jun and microglial activation were seen in the immobilised rats only. Cell death in the ventral horn was also noted in the immobilised rats. Conclusions. Immobilisation alone produces spinal cord changes in rats that indicate changes in central pro- cessing. This may explain some of the signs and symp- toms of patients with CRPS. doi:10.1016/j.ejpain.2007.03.389 375 VINCRISTINE-INDUCED NEUROPATHIC PAIN IN RATS: SPINAL CHANGES OF 5HT2A RECEP- TOR AND FOS EXPRESSION, AND MICRO- ARRAY ANALYSIS K. Thibault a,b , S. Dubacq b , M.J. Brisorgueil a , J. Fischer a , S. Pezet b , B. Calvino * ,b , M. Conrath a a Neurobiologie Des Signaux Intercellulaires, CNRS, UMR 7101, Universite ´ Pierre Et Marie Curie, France b CNRS UMR 7637, ESPCI, Paris, France Vincristine, a chemotherapeutic drug used to treat a wide variety of cancers has neurotroxic effects on peripheral sensory neurons, leading to severe neuro- pathic pain. Vincristine-induced neuropathic pain is characterized in humans by painful burning paresthe- sias, and dysesthesia in limb extremities, and hypersensi- tivity to noxious and non-noxious stimuli. In this study, we used an animal model of this neuropathic pain disor- der in the rat and studied the changes in 5-HT2A recep- tors and Fos expression in the spinal cord and DRGs in these animals at day 15 post-injection. We observed an increase in the number of Fos positive neurons in super- ficial (I–II), deep laminae (V–VI) and in lamina III. 5- HT2AR immunostaining increased in the whole lumbar dorsal horn, and in particular in layer II. In addition, the number of nociceptive DRG cells expressing the 5- HT2AR was also increased in Vincristine-treated ani- mals compared with controls. These results suggest that 5-HT, via the 5-HT2AR, could be involved (1) in the peripheral sensitization of nociceptors, (2) in a wide cen- tral sensitization affecting the majority of neurons in the whole lumbar dorsal horn. In a second part of this study, we analyzed changes in gene expression in the spinal cord of Vincristine-treated animals (compared with controls) using microarray S166 Poster Presentations / Animal studies – Systems / European Journal of Pain 11(S1) (2007) S59–S207