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. Author manuscript; available in PMC: 2009 Oct 1.
Published in final edited form as: J Neurogenet. 2008 Dec 19;23(1):185–199. doi: 10.1080/01677060802471726

Figure 1.

Figure 1

Focal loose patch-clamp recordings of excitatory junctional currents (ejcs) from WT and rut nerve terminals at larval neuromuscular junctions (NMJs). A. Configuration of loose patch-clamp recording of ejcs. A fire-polished micropipette was placed over the synaptic boutons to record focal ejcs evoked by nerve stimulation. Most recordings were performed on muscle 13 where type Ib and Is terminals run closely and the recording pipet covered both types of boutons (site ‘b’). Typically, type Is boutons traverse longer distance and type Is boutons could be recorded in isolation near the distal end of the terminal (site ‘a’). B. Ejc components from type Is (○) and Ib (●) synaptic boutons. When stimulated at a distant site from the NMJ (open arrow in A, see text), ejcs with two peaks were recorded at site ‘b’ but a single peak at site ‘a’, indicating that the 1st and 2nd peaks correspond to responses from type Is and Ib boutons, respectively. C. Separation of ejcs from type Ib and Is boutons at different stimulation intensities. The threshold of type Is axon was typically lower than that of type Ib axon and ejcs with two peaks appeared at site ‘b’ only at a higher stimulus intensity. D. Single-peak ejcs containing both type Ib and Is components were obtained when stimulation was applied closer to the nerve terminal (filled arrow in A). The shorter propagation distance did not significantly segregate the arrival time of action potential in type Is and Ib axons and the two ejc components completely overlapped. Superimposed traces demonstrate that rut ejcs were smaller and more variable under the same recording conditions. E. Amplitude distribution of focal ejcs in WT and rut. More than half of recording sites in rut NMJs produced ejcs smaller than 2 nA while the majority in WT yielded ejcs greater than 2 nA. In this study, the ejc size of 2 nA (arrow) was used to separate two distinct groups of axon terminals that exhibit high- and low-output transmission levels (see Figure 2A). N = 175 for WT and 130 for rut. F. Box plots comparing ejc amplitudes from type Ib and Is terminals between WT and rut. Arrow indicates an outlier beyond the scale. Numbers of recording sites were indicated. ***, p < 0.001; Mann-Whitney rank test with sequential Bonferroni adjustment.