Transient receptor potential (TRP) channels are pivotal in modulating vascular functions. In fact, topical application of cinnamaldehyde or capsaicin (TRPA1 and TRPV1 channel agonists, respectively) induces “local” changes in blood flow by releasing vasodilator neuropeptides. We investigated TRP channels’ contributions and the pharmacological mechanisms driving vasodilation in human isolated dermal arteries. Ex vivo studies assessed the vascular function of artery segments and analyzed the effects of different compounds. Concentration–response curves to cinnamaldehyde, pregnenolone sulfate (PregS, TRPM3 agonist), and capsaicin were constructed to evaluate the effect of the antagonists HC030031 (TRPA1); isosakuranetin (TRPM3); and capsazepine (TRPV1). Additionally, the antagonists/inhibitors olcegepant (CGRP receptor); L-NAME (nitric oxide synthase); indomethacin (cyclooxygenase); TRAM-34 plus apamin (K⁺ channels); and MK-801 (NMDA receptors, only for PregS) were used. Moreover, CGRP release was assessed in the organ bath fluid post-agonist-exposure. In dermal arteries, cinnamaldehyde- and capsaicin-induced relaxation remained unchanged after the aforementioned antagonists, while PregS-induced relaxation was significantly inhibited by isosakuranetin, L-NAME and MK-801. Furthermore, there was a significant increase in CGRP levels post-agonist-exposure. In our experimental model, TRPA1 and TRPV1 channels seem not to be involved in cinnamaldehyde- or capsaicin-induced relaxation, respectively, whereas TRPM3 channels contribute to PregS-induced relaxation, possibly via CGRP-independent mechanisms.

Dihydroergotamine (DHE) is an acute antimigraine agent that displays affinity for dopamine D2-like receptors, serotonin 5-HT1/2 receptors and α1/α2-adrenoceptors. Since activation of vascular α1/α2-adrenoceptors results in systemic vasopressor responses, the purpose of this study was to investigate the specific role of α1- and α2-adrenoceptors mediating DHE-induced vasopressor responses using several antagonists for these receptors. For this purpose, 135 male Wistar rats were pithed and divided into 35 control and 100 pretreated i.v. with ritanserin (100 μg/kg; to exclude the 5-HT2 receptor-mediated systemic vasoconstriction). Then, the vasopressor responses to i.v. DHE (1–3100 μg/kg, given cumulatively) were determined after i.v. administration of some α1/α2-adrenoceptor antagonists. In control animals (without ritanserin pretreatment), the vasopressor responses to DHE were: (i) unaffected after prazosin (α1; 30 μg/kg); (ii) slightly, but significantly, blocked after rauwolscine (α2; 300 μg/kg); and (iii) markedly blocked after prazosin (30 μg/kg) plus rauwolscine (300 μg/kg). In contrast, after pretreatment with ritanserin, the vasopressor responses to DHE were: (i) attenuated after prazosin (α1; 10 and 30 μg/kg) or rauwolscine (α2; 100 and 300 μg/kg); (ii) markedly blocked after prazosin (30 μg/kg) plus rauwolscine (300 μg/kg); (iii) attenuated after 5-methylurapidil (α1A; 30–100 μg/kg), L-765,314 (α1B; 100 μg/kg), BMY 7378 (α1D; 30–100 μg/kg), BRL44408 (α2A; 100–300 μg/kg), imiloxan (α2B; 1000–3000 μg/kg) or JP-1302 (α2C; 1000 μg/kg); and (iv) unaffected after the corresponding vehicles (1 ml/kg). These results suggest that the DHE-induced vasopressor responses in ritanserin-pretreated pithed rats are mediated by α1- (probably α1A, α1B and α1D) and α2- (probably α2A, α2B and α2C) adrenoceptors. These findings could shed light on the pharmacological profile of the vascular side effects (i.e. systemic vasoconstriction) produced by DHE and may lead to the development of more selective antimigraine drugs devoid vascular side effects.

Background and Purpose: Sex‐dependent vascular effects of transient receptor potential (TRP) channels and sex dimorphism in migraine are not yet fully characterized. We investigated the differential vasoactive effects of TRP ankyrin 1 (TRPA1), TRP melastatin 3 (TRPM3) and TRP vanilloid 1 (TRPV1) channels, their pharmacological mechanism(s), and localization and expression in human isolated blood vessels.Experimental Approach: Agonist responses to cinnamaldehyde (TRPA1), pregnenolone sulfate (PregS, TRPM3) or capsaicin (TRPV1) were analysed using wire myography in segments of human coronary (HCAs) and middle meningeal (HMMAs) arteries from men and women. The mechanisms involved in these responses were investigated using the antagonists/blockers/inhibitors: HC‐030031 (TRPA1), isosakuranetin (TRPM3), capsazepine (TRPV1), olcegepant (calcitonin gene‐related peptide [CGRP] receptor), L‐NAME (nitric oxide synthase [NOS]), indomethacin (cyclooxygenase [COX]), TRAM‐34 + apamin (K⁺ channels) or MK‐801 (N‐methyl‐d‐aspartate [NMDA] receptor). Fluorescence microscopy, quantitative polymerase chain reaction (qPCR), and western blotting were performed to investigate their location and expression, respectively.Key Results: In HCAs and HMMAs, (i) capsaicin‐induced relaxation remained unchanged after the above‐mentioned antagonists/blockers/inhibitors and (ii) cinnamaldehyde‐induced relaxation was blocked by olcegepant. PregS‐induced maximal relaxation was significantly enhanced in isolated arteries from females compared with males and was inhibited after isosakuranetin, MK‐801 or L‐NAME. TRPM3 mRNA and protein expression, along with NMDA protein levels, were higher in arteries from females than males.Conclusion and Implications: Modulation of vascular tone in HCAs and HMMAs by activation of TRPM3 is sex‐dependent, likely involving NMDA receptors. This represents a new therapeutic direction, targeting sex dimorphism in migraine and its related cardiovascular events.