Infralimbic medial prefrontal cortex alters electroacupuncture effect in animals with neuropathic chronic pain

Introduction: Morphological reorganization in the neural networks of the medial prefrontal cortex (mPFC) may be involved in the development of chronic neuropathic pain (NP). Objectives: We investigated whether inactivation and neurostimulation of the infralimbic division (IFL) of the mPFC alter electroacupuncture-induced analgesia (EIA) at 2 Hz and 2/100 Hz in animals with chronic NP. Methods: Wistar rats were submitted to chronic constrictor injury of the ischiadicus nerve (CCI). Von Frey and acetone tests were performed to evaluate mechanical or cold allodynia. Animals were submitted to electroacupuncture (EA) at 2 Hz and 2/100 Hz for 20 min. After EA, the IFL cortex synaptic contacts were inactivated by cobalt chloride (200 nL of 1.0 mM CoCl2). Neurostimulation of the IFL cortex was also performed at 20 mu A for 15 s, after EA, using a deep brain stimulation device. Results: EA at 2 Hz and 2/100 Hz attenuated mechanical or cold allodynia in CCI rats. Microinjection of CoCl2 into the IFL division of the mPFC blocked the EA effect. EA at 2 Hz and 2/100 Hz, in association with neurostimulation of the IFL cortex, attenuated mechanical and thermal allodynia. Conclusion: EA induces antinociception in CCI rats. The analgesia was potentiated in association with neurostimulation in the IFL division of the mPFC.