Characterisation of vertical cells in the superficial dorsal horn of the mouse spinal cord

We found that NPFF cells were mainly restricted to lamina I and II of the dorsal horn. Both viral and reporter strategies captured most pro-NPFF-immunoreactive neurons. However, the majority of the fluorescent labelled cells lacked pro-NPFF, and we found a large overlap with GRPR. Morphological reconstruction revealed that most pro-NPFF neurons were vertical cells but differed from GRPR neurons, in having a dendritic spine density that was twice as high. The majority of excitatory input to GRPR cells originated from other excitatory interneurons, including NPFF cells, although they receive minimal input from primary afferents. Electrophysiological recordings demonstrated that NPFF cells differed from GRPR cells in displaying a higher frequency of miniature EPSCs, being more electrically excitable and responding to a NPY Y1 receptor agonist. The properties of neurons that expressed both NPFF and GRPR were comparable to those expressing GRPR and differed from cells expressing NPFF only.