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. 2005 Sep 15;569(Pt 1):163–178. doi: 10.1113/jphysiol.2005.094805

Figure 2. Effects of stimulation on the probability of transmitter release.

Figure 2

A, representative electrophysiological recordings of mEPPs (bottom) and EPPs evoked by paired-pulse stimulation (top) in control (B) and stimulated NMJs. C, mean amplitude of the first EPP evoked by paired-pulse stimulation in control (black) and stimulated (grey) NMJs. Mean amplitude of EPPs was reduced in stimulated NMJs (P < 0.001, Student's t test; n = 9 frogs, n = 26 stimulated NMJs, 26 control NMJs). D, frequency histogram depicting the distribution of mEPP frequency in control (black) and stimulated (grey) NMJs. MEPP frequency of stimulated NMJs was shifted toward smaller values (P = 0.015, Student's t test) (n = 6 frogs, n = 19 stimulated NMJs, 18 control NMJs). E, mean amplitude of the second EPP evoked by paired-pulse stimulation in control (black) and stimulated (grey) NMJs. Mean amplitude of EPPs was reduced in stimulated NMJs (P < 0.001, Student's t test; n = 9 frogs, n = 26 stimulated NMJs, 26 control NMJs). F, frequency histogram depicting the distribution of paired-pulse facilitation in control (black) and stimulated (grey) NMJs. Paired-pulse facilitation of stimulated NMJs was shifted toward greater values (P = 0.032, Student's t test; n = 9 frogs, n = 26 stimulated NMJs, 26 control NMJs). G, postsynaptic nicotinic AChRs labelled with α-bungarotoxin coupled to Texas Red, showing the configuration of nerve terminals in control and stimulated CP muscles. Both muscle groups had nerve terminal morphology ranging from complex, with many branches, to very simple. No significant differences were found in NMJ length between control and stimulated NMJs (P = 0.420; Student's t test; n = 10 frogs, n = 152 stimulated NMJs, 123 control NMJs). H, frequency histogram depicting the distribution of synaptic efficacy (number of quanta of neurotransmitter per micrometre of NMJ length) in control (black) and stimulated (grey) NMJs. Synaptic efficacy of stimulated NMJs was shifted toward smaller values for first (P < 0.001; Mann-Whitney rank sum test) and second EPP (P = 0.002; Mann-Whitney rank sum test; N = 6 frogs, n = 19 stimulated NMJs, 15 control NMJs).