Fig. 2.

Morphological, electrophysiological and neurochemical features of interneurons in laminae I–II of the mouse dorsal horn. Top panel Morphological features of lamina II dorsal horn neurons observed in sagittal slices. Confocal images of neurons filled with neurobiotin showing vertical (green), radial (gray), central (blue) or islet (red) morphologies. Scale = 100 µm. Lower left panel Electrophysiological whole-cell patch-clamp recording of dorsal horn neurons. Firing pattern of dorsal horn neurons can be tonic, phasic, with a gap between spikes, or with one or no action potential upon depolarizing current injection. Traces in black display membrane potential at -20pA or at rehobase respectively. Superimposed blue traces are representative firing patterns observed at suprathreshold current injection. Value for hyperpolarizing and depolarizing currents are indicated. Lower right panel The proportions of excitatory and inhibitory interneurons in this region that belong to different neurochemical populations. The relationship to the different transcriptomic populations identified by Haring et al. (2018) is also shown. Note that the NKB neurokinin B, NTS neurotensin, CCK cholecystokinin, SP substance P, NPFF neuropeptide FF and GRP–GFP cells form largely non-overlapping populations of excitatory interneurons, although there is some overlap between NKB/NTS and CCK/SP populations [reproduced from Gutierrez-Mecinas et al. (2019a)]. The GRP–GFP cells are defined as those that express GFP in the BAC transgenic GRP::eGFP line. For inhibitory interneurons, there is overlap between the galanin/dynorphin (GAL/DYN) population and the neuronal nitric oxide synthase (NNOS) population, and this is shown in purple. Similarly, the GAL/DYN population overlaps with the NPY population, and this is shown in brown. There is limited overlap between NPY cells and both NNOS and parvalbumin (PV) cells, although this is not shown on the pie chart. Reproduced from Boyle et al. (2017)