Enhancement of synaptic transmission and nociceptive behaviour in HPC‐1/syntaxin 1A knockout mice following peripheral nerve injury

Abstract

Our previous analysis of HPC-1/syntaxin 1A knockout (KO) mice indicated that HPC-1/syntaxin 1A plays an important role in the synaptic plasticity of the hippocampus in vitro and learning behaviour in vivo. In order to gain further insights into the physiological functions of HPC-1/syntaxin 1A, we studied the changes in the plasticity of synaptic transmission in the superficial dorsal horn of the spinal cord following a peripheral nerve injury in HPC-1/syntaxin 1A KO and wild-type (WT) mice. The von Frey filament test revealed that partial ligation of the sciatic nerve caused neuropathic pain in both WT and KO mice. However, KO mice showed significant enhancement of mechanical allodynia as compared with WT mice. Tight-seal whole-cell recordings were obtained from neurons in the superficial dorsal horn of the spinal cord slices. Electrical stimulus-evoked excitatory postsynaptic currents (EPSCs), asynchronous EPSCs (aEPSCs) in the presence of strontium, and spontaneously occurring miniature EPSCs (mEPSCs) were analysed. Prior to peripheral nerve ligation, no significant differences were observed in the properties of evoked EPSCs, aEPSCs and mEPSCs in KO and WT mice. Seven-14 days after partial ligation, the amplitude of evoked EPSCs and the frequency of aEPSCs and mEPSCs in KO mice were significantly greater than those in WT mice; however, the amplitude of aEPSCs and mEPSCs remained unchanged in both groups. Enhanced allodynia behaviour and significant enhancement of excitatory synaptic transmission following peripheral nerve ligation in KO mice suggest that HPC-1/syntaxin 1A might play a role in synaptic plasticity in the nociceptive pathway.