Effects of Peripheral Nerve Injury on the Kinetics of Electrically Evoked GABA Receptor-mediated Currents in GABAergic and Non-GABAergic Neurons of the Spinal Dorsal Horn

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The neurotransmitters and neuromodulators implicated in the processing of sensory and nociceptive information, γ-aminobutyric acid (GABA) is of importance in the spinal dorsal horn (SDH) neurons. Decrease in GABAergic inhibitory synaptic transmission plays an important role in mechanisms of neuropathic pain (NeP). We hypothesized that functional and structural changes in GABA receptors of SDH may occur after peripheral injury (PNI). In the present study, using whole-cell patch-clamp recording, we characterized the GABA receptor-mediated currents (I_GABA) and GABA receptor-mediated inhibitory postsynaptic currents (GABA-IPSCs) recorded from SDH neurons, and investigated the effects of the sciatic nerve ligation on these currents in the glutamate decarboxylase (GAD) 67 green fluorescent protein (GAD67-GFP) knock-in mice. Furthermore, using the quantitative real-time PCR analysis, we evaluated alterations of the expression level of the GABA receptor subunits by the sciatic nerve ligation. We observed changes in I_GABA and GABA-IPSCs in both GFP-negative and positive neurons, and alterations of the expression level of the GABA_A receptor subunits, in SDH after the sciatic nerve ligation. Our results suggest that influences on the function and structure of GABAergic neuron in SDH by PNI may play an important role in the mechanism of NeP.