Evaluation of formalin-induced pain behavior and glutamate release in the spinal dorsal horn using in vivo microdialysis in conscious rats

Measurement of neurotransmitters in the spinal dorsal horn in conscious animals remains a technical challenge. here we applied concentric microdialysis to measure formalin-induced glutamate (glu) release in the ipsilateral dorsal horn in conscious,freely-moving rats. hind paw formalin injection induced flinching nociceptive behaviors accompanied by increased glu in the dorsal horn (maximum = 294%). both flinching and glu increase were prevented by morphine (3 mg/kg,s.c.). accordingly,concentric microdialysis is a sensitive technique for studying neurochemical modulation induced by pain and analgesics in the spinal dorsal horn of awake rats. measurement of glu provides information on modulation of excitatory signals. © 2012 the japanese pharmacological society.