The spinal gray matter region around the central canal, lamina X, is critically involved in somatosensory processing and visceral nociception. Although several classes of primary afferent fibers terminate or decussate in this area, little is known about organization and functional significance of the afferent supply of lamina X neurons. Using the hemisected ex vivo spinal cord preparation, we show that virtually all lamina X neurons receive primary afferent inputs, which are predominantly mediated by the high-threshold Aδ- fibers and C-fibers. In two-thirds of the neurons tested, the inputs were monosynaptic, implying a direct targeting of the population of lamina X neurons by the primary nociceptors. Beside the excitatory inputs, 48% of the neurons also received polysynaptic inhibitory inputs. A complex pattern of interactions between the excitatory and inhibitory components determined the output properties of the neurons, one-third of which fired spikes in response to the nociceptive dorsal root stimulation. In this respect, the spinal gray matter region around the central canal is similar to the superficial dorsal horn, the major spinal nociceptive processing area. We conclude that lamina X neurons integrate direct and indirect inputs from several types of thin primary afferent fibers and play an important role in nociception.
Spinal lamina X neurons integrate direct and indirect inputs from several types of thin primary afferent fibers, thus playing an important role in nociception.
aDepartment of Sensory Signaling, Bogomoletz Institute of Physiology, Kiev, Ukraine
bDepartment of Molecular Biophysics, Bogomoletz Institute of Physiology, Kiev, Ukraine
cInstituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
dNeuronal Networks Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
eKiev Academic University, Kiev, Ukraine
*Corresponding author. Address: Department of Molecular Biophysics, Bogomoletz Institute of Physiology, 4 Bogomoletz St, Kiev 01024, Ukraine. Tel.: +380442562426. E-mail address: firstname.lastname@example.org (V. Krotov).
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