Distribution of Spinal Sensitization Evoked by Inflammatory Pain Using Local Spinal Cord Glucose Utilization Combined with (3)H-Phorbol 12,13-Dibutyrate Binding in Rats

Aims. Hyperalgesia following tissue injury is induced by plasticity in neurotransmission. Few investigators have considered the ascending input which activates the superficial of spinal cord. The aim was to examine neurotransmission and nociceptive processing in the spinal cord after mustard-oil (MO) injection. Both in vitro and in vivo autoradiographs were employed for neuronal activity and transmission in discrete spinal cord regions using the (14)C-2-deoxyglucose method and (3)H-phorbol 12,13-dibutyrate ((3)H-PDBu) binding sites. Methods. To quantify the hyperalgesia evoked by MO, the flinching was counted for 60 min after MO (20%, 50 μL) injection in Wistar rats. Simultaneous determination of (14)C-2-deoxyglucose and (3)H-PDBu binding was used for a direct observation of neuronal/metabolic changes and intracellular signaling in the spinal cord. Results. MO injection evoked an increase in flinching for 60 min. LSCGU significantly increased in the Rexed I-II with (3)H-PDBu binding in the ipsilateral side of spinal cord. Discussion. We clearly demonstrated that the hyperalgesia is primarily relevant to increased neuronal activation with PKC activation in the Rexed I-II of the spinal cord. In addition, functional changes such as “neuronal plasticity” may result in increased neuronal excitability and a central sensitization.