Figure 7.

Neurotransmitter identification of scratch-specialized interneurons. A, Intracellular recording from an interneuron (Int) during caudal scratching, swimming, and flexion reflex motor patterns, monitored via the dD8 nerve. Blue bar indicates the period of swim-evoking stimulation; arrow indicates the moment of flexion reflex-evoking stimulation. B, Reconstruction of this interneuron, showing its soma and dendrites (blue), along with its axon and axon terminals (red); box indicates the region shown in C. C, Course followed by interneuron axon collateral (red); inset, association with Homer (green). Scale bar, 10 μm. D, Reconstruction of another scratch-specialized interneuron, showing its soma and dendrites (blue), along with its axon and axon terminals (red); box indicates the region shown in E, top. E, Top, Projected image showing branches of an axon collateral in the medial gray matter just ventral to the central canal; box indicates the region of terminals shown below. E, Bottom, Projected image showing NB and Homer immunoreactivity; two sets of panels (single optical sections) show two terminals associated with Homer (Ho; green), confirming this interneuron is excitatory. Scale bars: top, 10 μm; bottom, 1 μm.