Table 3 Studies on the role of CGRP in inflammatory pain
From: Calcitonin gene-related peptide and pain: a systematic review
Study | Objectives | Reported pain as part of phenotype | Method and sample size | Source of CGRP | Results | Duration of the investigated condition | Correlation between CGRP level and pain |
|---|---|---|---|---|---|---|---|
Geber, 2007 [1] | Evaluate pain, hyperalgesia and neurosecretory function in pain models with CAP and ES | Experimental pain: CAP and ES | Samples from dermal microdialysis taken from 10 healthy volunteers. Patients rated pain levels after CAP and ES stimulation | Blood (plasma) | CGRP increase was measured after CAP, not after ES | 2Â h | NR |
Hamed, 2011 [2] | Determine cutaneous innervation in burn patients with chronic pain | Chronic inflammatory skin pain | Skin biopsies from 12 patients and 33 controls suffering from unilateral injury, without pain | Tissue biopsies (skin) | Increase in CGRP density compared to controls | >24Â months | CGRP-levels were higher in patients with pain compared to controls |
Krämer, 2005 [3] | Explore effect of specific blockers of NEP (phosphoramidon) and ACE (captopril) on intensity of neurogenic inflammation | Experimental pain: ES | Samples from dermal microdialysis were taken from 8 healthy volunteers. Patients quantified pain sensation during electrical stimulation using VAS | Dermal microdialysis | CGRP release could be measured after phosphoramidon perfusion | 1 h | CGRP release did not correlate to pain ratings during phosphoramidon infusion |
Kwak, 2014 [4] | Evaluate CGRP’s effect on wound healing process in hypertrophic scar formation | Inflammatory pain in scars | Skin biopsies from 43 patients. Biopsies were taken from scars, and also from a normal skin area | Tissue biopsies (skin) | Increased CGRP-levels in scars compared to matched unburned skin | >12 months | Increased CGRP-levels in painful scar areas compared to normal skin |
Onuoha, 2001 [5] | Examine plasma CGRP levels in patients with burns | Inflammatory pain from burn | Plasma was obtained from 13 patients immediately on hospital admission and 24Â h after admission. 13 volunteers served as controls | Blood (plasma) | CGRP levels were higher on admission, 4.9 pmol/L and after 24Â h, 7.3 pmol/L, than in controls, 1.9 pmol/L | NR | NR |
Salomon, 2008 [6] | Evaluate CGRP-levels in AD patients during exacerbation and disease remission | Pruritus due to AD | Plasma from 49 patients and 32 healthy controls | Blood (plasma) | CGRP-levels were lower compared to healthy controls | Mean 20.75Â years (1-55years) | High CGRP concentrations correlated with severe pruritus |
Schmelz, 1997 [7] | Examine neuropeptide release in human skin elicited by histamine iontopheresis and topical CAP application | Experimental pain: histamine iontopheresis and CAP application | Samples from dermal microdialysis taken from 10 healthy volunteers. Patients were pain free prior start | Dermal microdialysis | CGRP concentration increased after histamine iontophoresis, but not capsaicin application | 3Â h | NR |
Simone, 1998 [8] | Determine whether hyperalgesia after intradermal injection of CAP could be attributed to morphological changes in ENF’s | Experimental pain: intradermal CAP injection | Skin biopsies from 8 healthy volunteers | Tissue biopsies (skin) | Complete loss of CGRP-fibers was observed 72 h after capsaicin injections. They reappeared 3–4 weeks after | 6 weeks | NR |