Fig. 4.

Sensitivity to block of P/Q channels with ω-agatoxin-IVA is similar in control endplates and endplates from muscle injected 4–5 days earlier with BTX. Black traces represent EPCs from a control and a BTX-blocked endplate prior to application of ω-agatoxin-IVA. Gray traces represent EPCs following block of P/Q channels by application of ω-agatoxin-IVA. In control muscle the mean reduction in EPC amplitude following block of P/Q channels was 75 ± 5%. In BTX-treated endplates the mean reduction in EPC amplitude was similar (80 ± 4%, P = 0.47, n = 4 muscles for control, 5 muscles for BTX). All EPCs were measured at a holding potential of −45 mV. Due to use of the same holding potential the EPCs following application of BTX were smaller and are shown at a higher gain.