Fig. 4. Two nonspiking interneurons that do not show GABA-immunofluorescence. (A) A nonspiking interneuron, viewed ventrally, with its cell body in the posterior lateral group. The cell body (arrow) appears green after merging the Lucifer-Yellow-fluorescence (green) and the Cy3/GABA-immunofluorescence (red), indicating the absence of GABA immunoreactivity. A few small neighbouring cell bodies are GABA-immunopositive (red). Two confocal planes each separated by 8.8 µm were combined to show the cell body, and seven further planes with the same spacing of the green alone were combined to show the fine primary neurite and neuropilar branches. Lateral nerve 5 (N5) is on the right. (B) The green cell body of an anterior lateral interneuron, indicating that it is not GABA-immunopositive (arrow); some other small cell bodies are red, indicating that they are immunopositive. Combined from two confocal planes separated by 4.5 µm. (C) Injecting a pulse of hyperpolarizing current into the interneuron shown in B causes an increase in the frequency of motor spikes recorded in the flexor tibiae muscle but has little effect on spikes in the slow extensor tibiae motor neuron or in an unidentified motor neuron in the coxa. Scale bars in A and B, 100 µm.

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