Identification of inhibitory interneuron revealed by slice patch and morphological approaches in spinal dorsal horn neurons

Abstract

To investigate whether neurons with different morphology have different inputs arose from primary afferent in substantia gelatinosa (SG) of the spinal dorsal horn, we performed whole cell recordings with patch pipettes filled with neurobiotin in a horizontal slice preparation of adult rat spinal cord with an attached dorsal root. Dorsal root stimulations revealed that most neurons recorded had evoked inhibitory postsynaptic currents (eIPSCs) that were mediated by GABAergic and/or glycinergic interneurons as well as monosynaptic and/or polysynaptic evoked excitatory postsynaptic currents (eEPSCs). Based on the dendritic arborization, there were at least four cell types (large islet, small islet, vertical and radial cell), and their morphological features were associated with characteristic inputs. Large islet and small islet cells received excitatory monosynaptic inputs by C-fiber, while radial and vertical cells received excitatory monosynaptic inputs by both A-δ and C-fibers. Aδ-fiber mediated eIPSCs were observed in all cell types. C-fiber mediated eIPSCs were not seen in large islet group although observed in other three groups. These results suggest that complex excitatory and inhibitory neuronal circuits originated from primary afferent are responsible for the processing of nociceptive information in SG. [Jpn J Physiol 55 Suppl:S161 (2005)]