Abstract: Objective To investigate the expression of BRD4 in the spinal cord and its relatiocontrolhip with acute inflammation pain induced by formaldehyde in mice. Methods Thirty-six mouse are randomly divided into three groups: control group, formaldehyde group and indomethacin+ formaldehyde group. 25μL 1% formaldehyde is injected into the right plantar to establish the acute inflammationpain model, while the indomethacin (20m g /kg) is injected intraperitoneally 1 hour before formaldehyde injection. Then, all the mice are video recored for 1h to observe the spontous pain. Then, cell localization of BRD4 in the spinal cord of Normal mice is determined by immunofluorescence assasy. The expression of BRD4 in spinal cord is detected by immunohistochemistry and western blot. Results Immunofluorescence showed that BRD4 is mainly co-locolized with the neuronal marker NeuN in the spinal cord of Normal mice. Formaldehyde injection could induce two-phase spontaneous pain, while indomethacin intervention could only decrease the second phase pain(P < 0.05). Furthermore, formaldehyde injection lead to significanlty enhanced expression of BRD4 in bilateral spinal cord, which is remarkbly inhibited by indomethacin(P < 0.05). Conclusions Upregulation of BRD4 in spinal dorsal horn may be involved in the acute inflammatory pain.

Key words: Bromodomain 4 (BRD4), spinal cord, formalin, neure, indomethacin