Miniature endplate potential frequency

Spontaneous release of acetylcholine, as measured electrophysiologically as increased miniature endplate potential (MEPP) frequency, was determined in myofibers from rat hemidiaphragms exposed to 2,4-DNP and/or methylmercury (Levesque and Atchison 1987). Tissues exposed to... 

Other potential antagonists of BoNT such as elevated calcium, calcium ionophores, lanthanum, black widow spider venom, 2,4-dinitrophenol, and agents that raise cyclic AMP levels were examined for their ability to reverse BoNT toxicity. Addition of the above compounds to BoNT-intoxicated preparations led to increases in the frequency of spontaneous miniature endplate potentials (MEPP) but resulted in little or no enhancement in the amplitude of evoked endplate potentials (EPP)." " Since these compounds generally increased spontaneous but not evoked activity, they were not considered to be of practical value for treatment of BoNT intoxication. 

This can be clearly seen by observing the change in the miniature endplate potential (MEPP). The MEPP is a very small potential, observed in the neuromuscular junction, that is due to the natural leakage of acetylcholine from the vesicle. When p-toxin is applied, the MEPP frequently decreases first (5-10 min), then suddenly increases (for several hours). Finally, the frequency decreases until it becomes zero. 

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