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Review
. 2011 Dec;152(12):2685-2689.
doi: 10.1016/j.pain.2011.08.004. Epub 2011 Sep 1.

The paradox of pain from tooth pulp: low-threshold "algoneurons"?

Kaj Fried  1 , Barry J Sessle, Marshall Devor
Affiliations
Review

The paradox of pain from tooth pulp: low-threshold "algoneurons"?

Kaj Fried et al. Pain. 2011 Dec.
No abstract available

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Conflict of interest statement

The authors declare no conflicts of interest with regard to this paper.

Figures

Fig. 1
Fig. 1. Many pulpal afferents are of medium and large-diameter, but express neurotransmitters typical of nociceptors
Images show pulpal afferent neurons in the rat TRG labeled with the tracer fluoro-gold (FG) that was applied to the dentin in the floor of shallow cavities in the mesial and lingual surfaces of the first and second maxillary molars. The cavities were sealed with a light-cured restorative material and after four weeks the TRGs were fixed, removed and processed for immunocytochemistry. A) Arrows show FG-labeled neurons of medium to large sizes (intrinsic fluorescence). B) shows the same field in Nomarski differential interference contrast (DIC) illumination. Many small-diameter neurons are present alongside medium and large neurons. Arrows point to the same neurons indicated in A. C) The same field immunolabeled using an antibody that recognizes CGRP. Many small afferents neurons are labeled, but also some of the medium and large dentinal afferents labeled with FG in panel A (arrows). D) None of the FG-labeled pulpal afferents bind IB4, a lectin associated with a subpopulation of small nociceptive neurons. (Photomicrographs kindly provided by Dr. John Naftel).
Fig. 2
Fig. 2. Individual pulpal neurons in the TRG may express both the nociceptor neurotransmitter CGRP and markers typical of LTMs
TRG neurons that innervate tooth pulp in rats were labeled by retrograde transport of FG and processed in the same way as described for Fig. 1. A) Five FG-labeled pulpal afferent neurons are shown (intrinsic fluorescence). B) shows the same field immunolabeled using an antibody that recognizes RT97, a marker of medium and large-diameter neuron that are mostly LTMs (Cy2 used as fluorochrome). Arrows indicate the FG-labeled neurons in A. All five express RT97. C) Two large-diameter FG-positive pulpal afferents in the TRG are shown at higher magnification. Both are RT97 immunopositive (arrows in D; Cy3 used as fluorochrome). F) Merging images C and E confirms that these large-diameter RT97 positive pulpal afferents also express CGRP. Scale bars: A,B = 50 μm; C-F = 50 μm.
See this image and copyright information in PMC

References

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