Heat hyperalgesia and mechanical hypersensitivity induced by calcitonin gene-related peptide in a mouse model of neurofibromatosis

S White, B Marquez de Prado, AF Russo… - PloS one, 2014 - journals.plos.org
S White, B Marquez de Prado, AF Russo, DL Hammond
PloS one, 2014journals.plos.org
This study examined whether mice with a deficiency of neurofibromin, a Ras GTPase
activating protein, exhibit a nociceptive phenotype and probed a possible contribution by
calcitonin gene-related peptide. In the absence of inflammation, Nf1+/− mice (B6. 129S6
Nf1/J) and wild type littermates responded comparably to heat or mechanical stimuli, except
for a subtle enhanced mechanical sensitivity in female Nf1+/− mice. Nociceptive phenotype
was also examined after inflammation induced by capsaicin and formalin, which release …
This study examined whether mice with a deficiency of neurofibromin, a Ras GTPase activating protein, exhibit a nociceptive phenotype and probed a possible contribution by calcitonin gene-related peptide. In the absence of inflammation, Nf1+/− mice (B6.129S6 Nf1/J) and wild type littermates responded comparably to heat or mechanical stimuli, except for a subtle enhanced mechanical sensitivity in female Nf1+/− mice. Nociceptive phenotype was also examined after inflammation induced by capsaicin and formalin, which release endogenous calcitonin gene-related peptide. Intraplantar injection of capsaicin evoked comparable heat hyperalgesia and mechanical hypersensitivity in Nf1+/− and wild type mice of both genders. Formalin injection caused a similar duration of licking in male Nf1+/− and wild type mice. Female Nf1+/− mice licked less than wild type mice, but displayed other nociceptive behaviors. In contrast, intraplantar injection of CGRP caused greater heat hyperalgesia in Nf1+/− mice of both genders compared to wild type mice. Male Nf1+/− mice also exhibited greater mechanical hypersensitivity; however, female Nf1+/− mice exhibited less mechanical hypersensitivity than their wild type littermates. Transcripts for calcitonin gene-related peptide were similar in the dorsal root ganglia of both genotypes and genders. Transcripts for receptor activity-modifying protein-1, which is rate-limiting for the calcitonin gene-related peptide receptor, in the spinal cord were comparable for both genotypes and genders. The increased responsiveness to intraplantar calcitonin gene-related peptide suggests that the peripheral actions of calcitonin gene-related peptide are enhanced as a result of the neurofibromin deficit. The analgesic efficacy of calcitonin gene-related peptide receptor antagonists may therefore merit investigation in neurofibromatosis patients.
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