Abnormal synaptic transmission at the neuromuscular junction Decreased miniature endplate potentials Decreased MEPP Small miniature endplate currents UMLS:C1853952 An abnormal reduction in the amplitude of the miniature endplate potentials, i.e. the postsynaptic response to transmitter released from an individual vesicle at the neuromuscular junction. Small miniature endplate potentials HP:0003402 Miniature end plate potentials are the small (about 0.5mV) depolarisations of the postsynaptic terminal caused by the release of a single vesicle into the synaptic cleft.