Answer: In electrophysiology, mini excitatory postsynaptic currents are recorded in bath applied tetrodotoxin, while spontaneous excitatory post synaptic currents are done in bath applied GABAA inhibitor.
MEPSCs and sEPSCs are both measures that examine the influence of excitatory neurotransmitters on a neuron. Both mEPSCs and sEPSCs are measured in a whole cell recording configuration. Because current is being recorded here, the experimenter must be in voltage clamp. The major difference is that in recording mEPSCs, the spontaneous activity of the network is eliminated due to the voltage-gated sodium channel inhibitor tetrodotoxin (TTX).
Inhibitory events can also be measured in this same way. The release of GABA is called an IPSC, or an inhibitory postsynaptic current. To measure sIPSCs, pharmacological inhibition of excitatory neurotransmitters must be performed, possible with DNQX or CNQX for blockade of AMPA type receptors, and APV for blockade of NMDA type receptors. Usually to measure inhibitory events, the cell must be clamped at a positive potential, or an internal solution containing a modified concentration of chloride must be used.
Deviations in membrane potential can also be measured in this way. The recording must be performed in a current clamp configuration for membrane potential to be measured. In this case, the events are called EPSPs, or excitatory postsynaptic potentials.
Spontaneous or miniature excitatory events are usually analyzed with software such as MiniAnalysis by Synaptosoft. They are generally difficult to identify since there may be multiple events at once. They generally have a much more rapid rise time with a slower time course of decay. Both frequency of events and amplitude of events are relevant physiologically. A change in presynaptic release mechanisms is often manifested as an increase in mEPSC frequency. A change in postsynaptic receptor expression or function is manifested as an increase in mEPSC amplitude.