抄録
We have recently reported that a phospholipase A2 (PLA2) activator melittin reversibly enhances glutamatergic excitatory synaptic transmission in substantia gelatinosa (SG; lamina II of Rexed) neurons of the rat spinal cord. The SG neurons receive not only excitatory but also GABA- and glycine-mediated inhibitory transmission. In order to know the effect of melittin on the spontaneous inhibitory transmission, we applied the blind whole-cell patch-clamp technique to SG neurons in adult rat spinal cord slices. Melittin (1 μM) superfused for 3 min gradually increased the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) at a holding potential of 0 mV, which were visible about 2 min after the beginning of its superfusion and subsided within 8 min after washout. These facilitatory actions of melittin were observed for GABAergic and glycinergic sIPSCs, which were recorded in the presence of a glycine-receptor antagonist strychnine (1 μM) and a GABAA receptor antagonist bicuculline (10 μM), respectively, and were reduced in extent by a PLA2 inhibitor 4-bromophenacryl bromide (10 μM). A voltage-gated Na+ channel blocker tetrodotoxin (TTX, 0.5 μM) had a tendency to inhibit the effect of melittin on the GABAergic but not glycinergic sIPSC. It is concluded that melittin enhances GABAergic and glycinergic inbibitory transmission in a pre- and postsynaptic manner through the activation of PLA2 in the SG; a part of the effect of melittin on GABAergic transmission is due to its action on excitatory transmission. [J Physiol Sci. 2006;56 Suppl:S162]
