Abstract: (9536 Views)
Introduction: Despite significant progress in understanding pain control mechanism, there are numerous questions
about central nervous mechanisms underlying stress-induced analgesia. The rostral ventromedial medulla (RVM) in the
brainstem integrates a variety of functions, including pain modulation and pain perception. In the present study, we
investigated the effect of temporary inactivation of RVM on stress-induced analgesia.
Methods: This study was performed using adult male Wistar rats (200-250 gr). Swim stress was induced using a
cylinder filled with water (50 cm height, 20±1°C) in which the rats were kept for 3 min. For induction of pain, 50 μL of
2% formalin was injected subcutaneously in the hind paw. For temporary inactivation of RVM, 0.5 μL of 2% lidocaine
was injected into RVM.
Results: Injection of lidocaine into RVM, before inducing swim stress, potentiated the anti-nociceptive effects of
swim stress in phase 1 and phase 2A. In phase 2B swim stresses increased nociceptive scores of formalin test so
administration of lidocaine into RVM inhibited the effect of swim stress.
Conclusion: The result of this study demonstrated that temporal inactivation of RVM by lidocaine potentiated
stress-induced analgesia.