The types of neuron which contain protein kinase C gamma in rat spinal cord

Protein kinase C (PKC) is thought to have a role in sensitization of dorsal horn neurons in certain pain states, and a recent study has reported that mice which lack the gamma isoform (PKC gamma) show reduced neuropathic pain after peripheral nerve injury. Although PKC gamma is present at high levels in the ventral part of lamina II we have Limited information concerning the types of neuron in which it is located. In this study we have used immunocytochemistry to characterise the neurons which contain PKC gamma. Immunoreactive neurons were concentrated in ventral lamina II, but were also present in lamina III. Some weakly-immunoreactive neurons were located in the dorsal part of lamina II and in lamina I. The great majority (92%) of cells with PKC gamma were not GABA-immunoreactive, and these cells are likely to be excitatory interneurons. Dual-immunofluorescence labelling showed that PKC gamma was not randomly distributed amongst non-GABAergic neurons, since it was present in 76% of cells with neurotensin and 45% of those with somatostatin, but only 5% of those with the mu-opioid receptor (MOR-1). Cells with the neurokinin 1 receptor are found in lamina I and lamina UI, and PKC gamma was present in 22% and 37% of these populations, respectively. These results suggest that excitatory interneurons in laminae II and III which lack the mu-opioid receptor may have a significant role in generating neuropathic pain. (C) 1999 Elsevier Science B.V. All rights reserved.