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. 2020 Mar 21;12(3):197. doi: 10.3390/toxins12030197

Figure 4.

Figure 4

αM-MIIIJ blocks excitatory postsynaptic potentials (EPSPs), miniature excitatory postsynaptic potentials (MEPSPs), and ACh-evoked postsynaptic potentials (PSPs) in X. laevis LP muscle. Intracellular recording from juvenile muscle preparation was performed as described in Methods. All responses were obtained contemporaneously from one muscle fiber whose resting potential ranged between −77 to −88 mV. A–C. Time course of block by 0.2 or 10 μM αM-MIIIJ of EPSPs (A), MEPSPs (B), and ACh-evoked PSPs (C). The pair of asterisks along the top of panel B denotes the time interval flanked by the pair of asterisks in panel A. Insets in panels A and C show sample traces before (1) and in the presence of 0.2 μM αM-MIIIJ (2) or 10 μM αM-MIIIJ (3). Hump in falling phase of EPSPs in inset of panel A presumably reflects the multiple innervation of the fiber. Sample traces in panel B were obtained before (left) and in the presence of 0.2 μM αM-MIIIJ (right); each trace shows two MEPSPs, and the calibration scale applies to both traces. No MEPSPs were discernable in the presence of 10 µM αM-MIIIJ. Early spike of superimposed traces in inset of C is an artifact of the iontophoretic pulse.