Figure 7.

Local axon collaterals arising from mouse SPBNs. (A and B) Images show examples of LI SPBN axon recovered from sagittal spinal cord slices after patch clamp recordings (dashed white line denotes white/gray matter border). A thin, consistent diameter process emanating from either the soma or a stem dendrite was classified as an axon. These axons were seen to give rise to collateral branches. A and B show maximum intensity z projections of a Neurobiotin-filled SPBNs (left) showing clear somatodendritic and axonal labelling (denoted by *). Scale bars = 50 μm and 10 μm for insets. Traced reconstruction of the SPBNs in A and B are also shown with somatodendritic profiles in white and axonal profiles in green to fully summarise the neuronal morphology and axonal territory. Insets show clear axonal branching points within the dorsal horn (left) and axons originating from the soma or a primary dendrite (right, arrows). (C) GFP-labelled SPBN axon including en passant boutons (arrows). Lower panels show high-magnification images of GFP expressing axon collaterals (from above) with vesicular glutamate transporter 2 (white) and Homer immunolabelling (purple). Vesicular glutamate transporter 2 is co-expressed in axon collaterals (middle) and closely apposed by Homer puncta (right) confirming functional synapses. SPBNs, spinoparabrachial projection neurons.