Dyngo-4a and cytochalasin D inhibit recovery from synaptic depression at the neuromuscular junction.

NMJ preparations were either incubated with dyngo-4a (30 µM) or cytochalasin D (4 µM) or left untreated for 40 min in normal Ringer's solution. Synaptic depression was induced by stimulation at 20 Hz for 10 min. (A) Time-course of mean amplitude of EPPs (expressed as percentage of the average of the first 10 EPPs) from 4 terminals during stimulation elicited at 20 Hz in control (black), dyngo-4a-treated (red) and cytochalasin D-treated (blue) preparations as indicated. The inset in (A) shows representative EPP traces at the indicated time points. (B) Comparison of the averaged EPP amplitudes at the indicated time and conditions. (C) Comparison of average time constants of the exponential fits performed on each synaptic depletion time-course in the indicated conditions. (n = 4). (D–F), EPPs were elicited by electrical stimulation at a frequency of 0.5 Hz following 20 Hz high-frequency depletion to monitor recovery of neurotransmission. (D) Time-course of mean EPP amplitudes from 3 terminals during stimulation elicited at 0.5 Hz in control, dyngo-4a-treated and cytochalasin D-treated preparations as indicated. The inset in (D) shows representative EPP traces at the indicated time points. (E) Comparison of the rate of recovery of neurotransmission from synaptic depletion for the indicated conditions. (n = 3). Data shown as mean ± S.E.M and statistical significance was determined using Student's t test.