The effect of microinjection of dimethyl sulfoxide into the rostral ventromedial medulla on swim stress-induced analgesia

Abstract

Background: Dimethyl sulfoxide (DMSO) is an important solvent for compounds that used in pain research. Rostral ventromedial medulla (RVM) plays an important role in modulating nociception and stress-induced analgesia (SIA). Objective: The aim of this study was to investigate the effect of DMSO administration into the RVM on SIA by using formalin test. Methods: This experimental study was conducted on 27 Wistar male rats (200±30 gr) were randomly assigned to control, stress and stress+DMSO groups. Animals were placed in a water reservoir (20±1°C) for 3 minutes to induce forced swimming stress. Stereotaxic surgery was performed to microinjection of DMSO (0.5μl, 100%) into RVM. The pain behavior score was evaluated by subcutaneous injection of formalin 2% in the dorsal plantar region of hid paw. Findings: The pain score of phase 1, interphase and phase 2 of formalin test in swim stress group decreased significantly in comparison to control group (P