Presynaptic inhibitory action of morphine on excitatory synaptic transmission in rat SON neurons in brain slices

AIM To observe the effects of morphine on the excitatory postsynaptic currents (EPSCs) and miniature EPSCs (mEPSCs) in rat supraoptic nucleus (SON) neurons and to determine its synaptic mechanism. METHODS Using whole cell voltage clamp recording technique in brain slices, the EPSCs and mEPSCs of rat SON neurons were recorded, respectively. RESULTS 20 μmol·L -1 morphine decreased the frequency of EPSCs and mEPSCs (EPSCs by 65%, mEPSCs by 45%), and decreased the amplitude of EPSCs by 44% in all SON neurons, but had no effect on the amplitude distribution of mEPSCs. CONCLUSION Morphine inhibits the excitatory transmissions via presynaptic mechanisms in SON neurons from rat brain slices.