Spinal dorsal horn neurone targets for nociceptive primary afferents: do single neurone morphological characteristics suggest how nociceptive information is processed at the spinal level

2004 ◽  
Vol 46 (2) ◽  
pp. 173-190 ◽  
Author(s):  
Richard Morris ◽  
Ornsiri Cheunsuang ◽  
Anika Stewart ◽  
David Maxwell
Keyword(s):  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Morphological Characteristics ◽  
Primary Afferents ◽  
Spinal Level ◽  
Dorsal Horn Neurone ◽  
Spinal Dorsal ◽  
Nociceptive Information

scholarly journals Prior perineural or neonatal treatment with capsaicin does not alter the development of spinal microgliosis induced by peripheral nerve injury

2020 ◽  
Author(s):  
Ivett Dorina Szeredi ◽  
Gábor Jancsó ◽  
Orsolya Oszlács ◽  
Péter Sántha
Keyword(s):  
Peripheral Nerve ◽  
Dorsal Horn ◽  
Nerve Injury ◽  
Peripheral Nerve Injury ◽  
Spinal Dorsal Horn ◽  
Primary Afferents ◽  
Primary Afferent ◽  
Spinal Dorsal ◽  
C Fiber ◽  
Spinal Afferents

Abstract Peripheral nerve injury is associated with spinal microgliosis which plays a pivotal role in the development of neuropathic pain behavior. Several agents of primary afferent origin causing the microglial reaction have been identified, but the type(s) of primary afferents that release these mediators are still unclear. In this study, specific labeling of C-fiber spinal afferents by lectin histochemistry and selective chemodenervation by capsaicin were applied to identify the type(s) of primary afferents involved in the microglial response. Comparative quantitative morphometric evaluation of the microglial reaction in central projection territories of intact and injured peripheral nerves in the superficial (laminae I and II) and deep (laminae III and IV) spinal dorsal horn revealed a significant, about three-fold increase in microglial density after transection of the sciatic or the saphenous nerve. Prior perineural treatment of these nerves with capsaicin, resulting in a selective defunctionalization of C-fiber afferent fibers failed to affect spinal microgliosis. Similarly, peripheral nerve injury-induced increase in microglial density was unaffected in rats treated neonatally with capsaicin known to result in a near-total loss of C-fiber dorsal root fibers. Perineural treatment with capsaicin per se did not evoke a significant increase in microglial density. These observations indicate that injury-induced spinal microgliosis may be attributed to phenotypic changes in injured myelinated primary afferent neurons, whereas the contribution of C-fiber primary sensory neurons to this neuroimmune response is negligible. Spinal myelinated primary afferents may play a hitherto unrecognized role in regulation of neuroimmune and perisynaptic microenvironments of the spinal dorsal horn.

scholarly journals Electrophysiological and Morphological Features of Rebound Depolarization Characterized Interneurons in Rat Superficial Spinal Dorsal Horn

2021 ◽  
Vol 15 ◽  
Author(s):  
Mengye Zhu ◽  
Yi Yan ◽  
Xuezhong Cao ◽  
Fei Zeng ◽  
Gang Xu ◽  
...  
Keyword(s):  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Morphological Characteristics ◽  
Substantia Gelatinosa ◽  
Morphological Properties ◽  
Specific Cell ◽  
Membrane Hyperpolarization ◽  
Spinal Dorsal ◽  
C Fibers ◽  
Somatosensory Information

Substantia gelatinosa (SG) neurons, which are located in the spinal dorsal horn (lamina II), have been identified as the “central gate” for the transmission and modulation of nociceptive information. Rebound depolarization (RD), a biophysical property mediated by membrane hyperpolarization that is frequently recorded in the central nervous system, contributes to shaping neuronal intrinsic excitability and, in turn, contributes to neuronal output and network function. However, the electrophysiological and morphological properties of SG neurons exhibiting RD remain unclarified. In this study, whole-cell patch-clamp recordings were performed on SG neurons from parasagittal spinal cord slices. RD was detected in 44.44% (84 out of 189) of the SG neurons recorded. We found that RD-expressing neurons had more depolarized resting membrane potentials, more hyperpolarized action potential (AP) thresholds, higher AP amplitudes, shorter AP durations, and higher spike frequencies in response to depolarizing current injection than neurons without RD. Based on their firing patterns and morphological characteristics, we propose that most of the SG neurons with RD mainly displayed tonic firing (69.05%) and corresponded to islet cell morphology (58.82%). Meanwhile, subthreshold currents, including the hyperpolarization-activated cation current (Ih) and T-type calcium current (IT), were identified in SG neurons with RD. Blockage of Ih delayed the onset of the first spike in RD, while abolishment of IT significantly blunted the amplitude of RD. Regarding synaptic inputs, SG neurons with RD showed lower frequencies in both spontaneous and miniature excitatory synaptic currents. Furthermore, RD-expressing neurons received either Aδ- or C-afferent-mediated monosynaptic and polysynaptic inputs. However, RD-lacking neurons received afferents from monosynaptic and polysynaptic Aδ fibers and predominantly polysynaptic C-fibers. These findings demonstrate that SG neurons with RD have a specific cell-type distribution, and may differentially process somatosensory information compared to those without RD.

Unmyelinated primary afferents from adjacent spinal nerves intermingle in the spinal dorsal horn: A possible mechanism contributing to neuropathic pain

2008 ◽  
Vol 1208 ◽  
pp. 111-119 ◽  
Author(s):  
Safa A.S. Shehab ◽  
Khadija Al-Marashda ◽  
Amal Al-Zahmi ◽  
Afaf Abdul-Kareem ◽  
Mahmood A.H. Al-Sultan
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Primary Afferents ◽  
Spinal Nerves ◽  
Spinal Dorsal
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