Background Calcitonin gene-related peptide plasma levels have frequently been determined as a biomarker for primary headaches. However, published data is often inconsistent resulting from different methods that are not precisely described in most studies. Methods We applied a well-proven enzyme-linked immunosorbent assay to measure calcitonin gene-related peptide concentrations in human blood plasma, we modified parameters of plasma preparation and protein purification and used calcitonin gene-related peptide-free plasma for standard solutions, which are described in detail. Results Calcitonin gene-related peptide levels are stable in plasma with peptidase inhibitors and after deep-freezing. Calcitonin gene-related peptide standard solutions based on synthetic intercellular fluid or pooled plasma with pre-absorbed calcitonin gene-related peptide influenced the measurements but yielded both comprehensible results. In a sample of 56 healthy subjects the calcitonin gene-related peptide plasma levels varied considerably from low (<50 pg/mL) to very high (>500 pg/mL) values. After a 12-hour exposure of these subjects to normobaric hypoxia the individual calcitonin gene-related peptide levels remained stable. Conclusion Buffering with peptidase inhibitors and immediate freezing or processing of plasma samples is essential to achieve reliable measurements. Individuals show considerable differences and partly high calcitonin gene-related peptide plasma levels without detectable pathological reason. Thus plasma measurements are suited particularly to follow calcitonin gene-related peptide levels in longitudinal studies. The use of data for this study was approved by the Ethics Committee of the Medical University of Innsbruck ( https://www.i-med.ac.at/ethikkommission/ ; EK Nr: 1242/2017).

Here we directly demonstrate the liberation of CGRP from rat skin in vitro induced by high extracellular concentrations of KCl. The EC50 was 52 mM KCl and saturation was reached from 80 mM KCl. The release was entirely dependent on the presence of extracellular calcium ions. It was reduced by nonsubtype selective inhibition of voltage-operated calcium channels (VOCCs). Application of selective antagonists suggest expression of L-type and N-type but not P/Q-type VOCCs in cutaneous nociceptive terminals. These may be activated by any suprathreshold depolarizing stimuli to induce neurogenic inflammation. The expression pattern greatly differs from central nociceptive terminals where, in addition, P/Q-type VOCC have been found.

Monoclonal antibodies directed against the neuropeptide calcitonin gene-related peptide (CGRP) belong to a new generation of therapeutics that are effective in the prevention of migraine. CGRP, a potent vasodilator, is strongly implicated in the pathophysiology of migraine, but its role remains to be fully elucidated. The hemisected rat head preparation and laser Doppler flowmetry were used to examine the effects on CGRP release from the dura mater and meningeal blood flow of the subcutaneously injected anti-CGRP monoclonal antibody fremanezumab at 30 mg/kg, when compared to an isotype control antibody. Some rats were administered glycerol trinitrate (GTN) intraperitoneally to produce a migraine-like sensitized state. When compared to the control antibody, the fremanezumab injection was followed by reduced basal and capsaicin-evoked CGRP release from day 3 up to 30 days. The difference was enhanced after 4 h of GTN application. The samples from the female rats showed a higher CGRP release compared to that of the males. The increases in meningeal blood flow induced by acrolein (100 µM) and capsaicin (100 nM) were reduced 13–20 days after the fremanezumab injection, and the direct vasoconstrictor effect of high capsaicin (10 µM) was intensified. In conclusion, fremanezumab lowers the CGRP release and lasts up to four weeks, thereby lowering the CGRP-dependent meningeal blood flow. The antibody may not only prevent the released CGRP from binding but may also influence the CGRP release stimulated by noxious agents relevant for the generation of migraine pain.

The presence of neuropeptide-containing sensory, parasympathetic and sympathetic nerves in human nasal mucosa is well established. However, information regarding the neuropeptide distribution in nasal polyps is still lacking. The aim of this study was to compare immunohistologically the presence and distribution of substance P (SP), vasoactive intestinal peptide (VIP) and bombesin-flanking peptide (BFP) in normal nasal mucosa and nasal polyps. The expression was studied using Formalin-fixed and paraffin-embedded biopsy sections from 20 patients with nasal polyps and 10 controls with normal nasal mucosa from the anterior part of the inferior turbinate. Indirect immunohistochemistry (APAAP method) with mono- and polyclonal antibodies was used. None of the control group but 5 patients of the nasal polyp group had an atopic disease. Comparing localization and intensity of the immunohistological reaction in nasal mucosa and nasal polyp tissue, there was no difference in the expression of the three neuroendocrine substances. There was no difference of expression in the polyposis group itself concerning allergic and nonallergic subjects. The results indicate that VIP, SP and BFP have an equal distribution in nasal polyps and normal nasal mucosa.

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