No abstract

The spinal dorsal horn harbors a sophisticated and heterogeneous network of excitatory and inhibitory neurons that process peripheral signals encoding different sensory modalities. Although it has long been recognized that this network is crucial both for the separation and the integration of sensory signals of different modalities, the molecular identity of the underlying neurons and signaling mechanisms are still only partially understood. Here, we have used the translating ribosome affinity purification (TRAP) technique to map the translatomes of excitatory glutamatergic (VGLUT2 + ) and inhibitory GABA and/or glycinergic (VGAT + or Gad67 + ) neurons of the mouse spinal cord. Our analyses demonstrate that inhibitory and excitatory neurons are primarily set apart by the expression of genes encoding transcription factors or genes related to the production, release or re-uptake of their principal neurotransmitters (glutamate, GABA or glycine). Subsequent gene ontology (GO) term analyses revealed that neuropeptide signaling-related GO terms were highly enriched in the excitatory population. Eleven neuropeptide genes displayed largely non-overlapping expression patterns closely adhering to the laminar and hence also functional organization of the spinal cord grey matter, suggesting that they may serve as major determinants of modality-specific processing. Since this modality-specific processing of sensory input is severely compromised in chronic, especially neuropathic, pain, we also investigated whether peripheral nerve damage changes the neuron typespecific translatome. In summary, our results suggest that neuropeptides contribute to modalityspecific sensory processing in the spinal cord but also indicate that altered sensory encoding in neuropathic pain states occurs independent of major translatome changes in the spinal neurons.The ability to sense and discriminate different noxious and innocuous somatosensory stimuli is essential for all higher animals and humans in order to react adequately to external stimuli and internal conditions [1,2]. The spinal dorsal horn, i.e., the sensory part of the spinal cord, constitutes a key element in this process. It receives somatosensory signals from peripheral neurons and processes these signals together with other inputs descending from supraspinal sites in a complex network of inhibitory and excitatory interneurons before relaying these signals via projection neurons to supraspinal centers [3]. Projection neurons make up less than 10% of all dorsal horn neurons, while more than 90% of the neuronal population are interneurons of which, between 60 and 70% are excitatory glutamatergic neurons, and the rest is inhibitory (GABA and/or glycinergic).The spinal cord is organized in a laminar fashion, which has initially been proposed on the basis of differences in cell density and morphology between the different laminae [4, 5] but has later been shown to also reflect functional organization. This is especially reflected for example by the lamina specific innervation pattern by ...