Epidermal Nerve Fibers in Neuropathic Pain Model

Re-innervation in spared nerve injury (SNI) vs normal rats
Neuromics' Pain and Inflammation Research Antibodies are frequently used to help researchers find root causes of neuropathic pain. This is a fascinating study of re-innervation patterns of epidermal and dermal nerve fibers in a rat neuropathic pain model (Note: our Guinea Pig Polyclonal P2X3 Antibody was used in this study): Liron S. Durakua, Mehdi Hossaini, Barthold N. Schüttenhelm, b, Joan C. Holstege, Martijn Baas, Tom J.H. Ruigrok, Erik T. Walbeehm. Re-innervation patterns by peptidergic Substance-P, non-peptidergic P2X3, and myelinated NF-200 nerve fibers in epidermis and dermis of rats with neuropathic pain. Experimental Neurology Volume 241, March 2013, Pages 13–24. doi.org/10.1016/j.expneurol.2012.11.029.

Non-footpad area vs. footpad.The distribution pattern between the center non-footpad area and footpad is compared for the different subgroups of sensory skin fibers. For epidermal Sub P-IR and upper dermal NF-200-IR fibers there is an equal density of fibers in the center and footpad area suggesting a homogenous distribution over the foot sole of a rat. Whereas for epidermal P2X3-IR fibers there is a significant lower number of P2X3-IR fibers in the footpads as compared to the center non-footpad area, suggesting a heterogeneous distribution in the foot sole for this type of sensory fibers. N = 5 per group. Unpaired t-test. ***: p < 0,001. Scale bar: 250 μm. doi.org/10.1016/j.expneurol.2012.11.029

Illustration of the skin innervation in normal and SNI situation.Illustration showing the innervation pattern of subgroups of sensory skin fibers in the normal situation and in the SNI model 10 weeks PO. In the naïve animals the peptidergic CGRP and non-peptidergic P2X3 fibers have a lower density in the footpads as compared to the non-footpad areas, while the Substance P and NF-200 fibers have an equal distribution over the complete foot sole. In the SNI model there is a significant increase of CGRP epidermal fibers in the medial and lateral area of the foot sole and there is a complete re-innervation of the center area. In addition the footpads in the SNI model are hyper-innervated with CGRP fibers. Substance P and P2X3 and NF-200 fibers show no increased density in the uninjured medial and lateral area after 10 weeks PO. In addition, Substance P and P2X3 fibers hardly re-innervate the center area; however, the NF-200 fibers have the same density of fibers in the denervated area as in the normal situation. In the SNI model the medial, center and lateral area have all an increase in LC's, with the center area being the most prominent one. In addition the epidermis thickness of the SNI model has decreased significantly in all the three areas after 10 weeks PO.
Related Postings: http://neuromics.blogspot.com/search/label/Neuropathic%20Pain.

P2X3 Receptors and Cool Science

Our P2X3 Receptor Antibodies are widely used and frequently published. This publication references use of our P2X3 Guinea Pig Antibody.

I like the "cool factor" in this study: Ji Z-G , Ito S , Honjoh T , Ohta H , Ishizuka T , et al. 2012 Light-evoked Somatosensory Perception of Transgenic Rats That Express Channelrhodopsin-2 in Dorsal Root Ganglion Cells. PLoS ONE 7(3): e32699. doi:10.1371/journal.pone.0032699.-"We have recently generated several transgenic lines of rat in which channelrhodopsin-2 (ChR2) transgene is driven by the Thy-1.2 promoter. In one of them, W-TChR2V4, some neurons were endowed with photosensitivity by the introduction of the ChR2 gene, coding an algal photoreceptor molecule. The DRG neurons expressing ChR2 were immunohistochemically identified using specific antibodies to the markers of mechanoreceptive or nociceptive neurons. Their peripheral nerve endings in the plantar skin as well as the central endings in the spinal cord were also examined. We identified that ChR2 is expressed in a certain population of large neurons in the DRG of W-TChR2V4. On the basis of their morphology and molecular markers, these neurons were classified as mechanoreceptive but not nociceptive. ChR2 was also distributed in their peripheral sensory nerve endings, some of which were closely associated with CK20-positive cells to form Merkel cell-neurite complexes or with S-100-positive cells to form structures like Meissner's corpuscles. These nerve endings are thus suggested to be involved in the sensing of touch. Each W-TChR2V4 rat showed a sensory-evoked behavior in response to blue LED flashes on the plantar skin. It is thus suggested that each rat acquired an unusual sensory modality of sensing blue light through the skin as touch-pressure. This light-evoked somatosensory perception should facilitate study of how the complex tactile sense emerges in the brain."

The researchers used Blue LED light to fire neurons involved somatosensory or tactile response!

Images. Distribution of ChR2V in the dorsal part of the spinal cord. A–C. Immunohistochemical localizationof ChR2V with the cell-type specific markers, NF200 (A), CGRP (B) or P2X3 (C). Scale bars indicate 40 µm.

Note that the receptors involved in Nociceptive Pain Sensing do not overlap with ChR2V. From this the authors conclude that ChR2V is involved in mechanoreception. This rat model should facilitate future study of how complex tactile perception, such as for texture, size and shape, is generated. We will keep you posted.

In the meantime check out our markers and antibodies for studying Neurotransmission and Synaptic Mechanisms.