P2X3 receptor mediates ectopic mechanical allodynia with inflamed lower lip in mice.

Abstract

Ectopic pain in other orofacial regions develops with local inflammation in separated orofacial structures. However, the basis for the spreading of pain to adjacent orofacial areas after local inflammation is still unknown. In the present study, we determined if the P2X(3) receptor (P2X(3)R) was associated with altered mechanical sensitivity of the whisker pad skin following complete Freund's adjuvant (CFA) injection into the lower lip. Mice with local inflammation induced by CFA injection into the lower lip demonstrated significant mechanical allodynia of whisker pad skin. The mechanical allodynia was reversed by P2X(3)R antagonist, A-317491 administration into whisker pad skin. The number of P2X(3)R and calcitonin gene-related peptide (CGRP) positive trigeminal ganglion (TG) neurons that innervates the whisker pad skin and lower lip was increased after CFA injection into the lower lip. CGRP protein expression in TG ipsilateral to CFA injection was also significantly greater than that of the saline-injected mice. The present findings suggest that induced CGRP by local inflammation in the lower lip increases P2X(3)R in TG neurons, the increased P2X(3)Rs are involved in the sensitization of primary afferent neurons in the whisker pad skin. This P2X(3)R overexpression may underlie ectopic mechanical allodynia in the whisker pad skin after CFA injection into the lower lip.

• Authors: Masafumi Yasuda, Masamichi Shinoda, Masaaki Kiyomoto, Kuniya Honda, Azumi Suzuki, Takaaki Tamagawa, Kaori Kaji, Shigenari Kimoto, Koichi Iwata
• Journal: Neuroscience letters (Neurosci Lett) Vol. 528 Issue 1 Pg. 67-72 (Oct 18 2012) ISSN: 1872-7972 [Electronic] Ireland
• PMID: 22981884 (Publication Type: Journal Article)
• Copyright: Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Receptors, Purinergic P2X3
• Freund's Adjuvant
• Calcitonin Gene-Related Peptide

Topics

• Animals
• Calcitonin Gene-Related Peptide (metabolism)
• Cheilitis (chemically induced, metabolism)
• Freund's Adjuvant (toxicity)
• Hyperalgesia (metabolism)
• Immunohistochemistry
• Inflammation (chemically induced, metabolism)
• Lip
• Male
• Mice
• Mice, Inbred C57BL
• Pain, Referred (chemically induced, metabolism)
• Receptors, Purinergic P2X3 (metabolism)
• Skin (innervation)
• Vibrissae (innervation)