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Article Dans Une Revue Pain Année : 2015

Subpopulations of PKCγ interneurons within the medullary dorsal horn revealed by electrophysiologic and morphologic approach

Cristina Alba-Delgado
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Corinne El Khoueiry
Cédric Peirs
Alain Artola
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Myriam Antri

Résumé

Mechanical allodynia, a cardinal symptom of persistent pain, is associated with the unmasking of usually blocked local circuits within the superficial spinal or medullary dorsal horn (MDH) through which low-threshold mechanical inputs can gain access to the lamina I nociceptive output neurons. Specific interneurons located within inner lamina II (IIi) and expressing the gamma isoform of protein kinase C (PKCγ⁺) have been shown to be key elements for such circuits. However, their morphologic and electrophysiologic features are still unknown. Using whole-cell patch-clamp recordings and immunohistochemical techniques in slices of adult rat MDH, we characterized such lamina IIi PKCγ⁺ interneurons and compared them with neighboring PKCγ⁻ interneurons. Our results reveal that PKCγ⁺ interneurons display very specific activity and response properties. Compared with PKCγ⁻ interneurons, they exhibit a smaller membrane input resistance and rheobase, leading to a lower threshold for action potentials. Consistently, more than half of PKCγ⁺ interneurons respond with tonic firing to step current. They also receive a weaker excitatory synaptic drive. Most PKCγ⁺ interneurons express Ih currents. The neurites of PKCγ⁺ interneurons arborize extensively within lamina IIi, can spread dorsally into lamina IIo, but never reach lamina I. In addition, at least 2 morphologically and functionally different subpopulations of PKCγ⁺ interneurons can be identified: central and radial PKCγ⁺ interneurons. The former exhibit a lower membrane input resistance, rheobase and, thus, action potential threshold, and less PKCγ⁺ immunoreactivity than the latter. These 2 subpopulations might thus differently contribute to the gating of dorsally directed circuits within the MDH underlying mechanical allodynia.
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Dates et versions

hal-04326290 , version 1 (06-12-2023)

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Cristina Alba-Delgado, Corinne El Khoueiry, Cédric Peirs, Radhouane Dallel, Alain Artola, et al.. Subpopulations of PKCγ interneurons within the medullary dorsal horn revealed by electrophysiologic and morphologic approach. Pain, 2015, 156 (9), pp.1714-1728. ⟨10.1097/j.pain.0000000000000221⟩. ⟨hal-04326290⟩

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