Figure 3.

BChE inhibition depresses ACh release at the NMJ. A, Experimental protocol. The muscle contraction was blocked by inhibition of the muscle voltage-gated sodium channels with μ-conotoxin GIIIB. A sharp electrode was inserted close to a NMJ to record focal mEPPs and EPPs. A first file was obtained for the mEPPs (no nerve stimulation), then a second for the EPP (0.5 Hz nerve stimulations), and then a third for the mEPPs (no stimulation). Iso-OMPA (50 μm) was added to the Ringer's buffer and the muscle was stimulated indirectly at 0.1 Hz during the incubation. The electrode was maintained in place. All of the records were obtained in 30–40 min. The QC was obtained by dividing the mean amplitude of the EPPs by the mean amplitude of the mEPPs recorded before and after the EPPs if the resting membrane potential (RMP) did not change >1 mV during mEPP and EPP recording. B, Quantification of the QC in the same muscle fiber after inhibition of BChE with iso-OMPA. The percentage of decrease of the QC in WT mice is higher than in BChE KO mice (n = 5, *p < 0.05, paired Student's t test). C, The mean QC in the NMJs of WT mice is higher than in BChE KO mice (n = 20, *p < 0.05, and n = 5, *p < 0.05, respectively, unpaired Student's t test). D, Quantification of the QC in the same muscle fiber after inhibition of BChE with iso-OMPA when AChRs are absent or blocked. The graph presents the quantification of the QC in the same muscle fiber after iso-OMPA. All of the muscarinic receptors were blocked with 1 μm atropine (n = 5, *p < 0.05, paired Student's t test).