Perivascular Calcitonin Gene-related Peptide Research Articles

Vascular actions of peripheral CGRP in migraine-like photophobia in mice.

Calcitonin gene-related peptide is recognized as a key player in migraine, yet the mechanisms and sites of calcitonin gene-related peptide action remain unknown. The efficacy of calcitonin gene-related peptide-blocking antibodies as preventative migraine drugs supports a peripheral site of action, such as the trigeminovasculature. Given the apparent disconnect between the importance of vasodilatory peptides in migraine and the prevailing opinion that vasodilation is an epiphenomenon, the goal of this study was to test whether vasodilation plays a role in calcitonin gene-related peptide-induced light aversive behavior in mice. Systemic mean arterial pressure and light aversive behavior were measured after intraperitoneal administration of calcitonin gene-related peptide and vasoactive intestinal peptide in wild-type CD1 mice. The functional significance of vasodilation was tested by co-administration of a vasoconstrictor (phenylephrine, endothelin-1, or caffeine) with calcitonin gene-related peptide to normalize blood pressure during the light aversion assay. Both calcitonin gene-related peptide and vasoactive intestinal peptide induced light aversion that was associated with their effect on mean arterial pressure. Notably, vasoactive intestinal peptide caused relatively transient vasodilation and light aversion. Calcitonin gene-related peptide-induced light aversion was still observed even with normalized blood pressure. However, two of the agents, endothelin-1 and caffeine, did reduce the magnitude of light aversion. We propose that perivascular calcitonin gene-related peptide causes light-aversive behavior in mice by both vasomotor and non-vasomotor mechanisms.

Vasorelaxation to the Nitroxyl Donor Isopropylamine NONOate in Resistance Arteries Does Not Require Perivascular Calcitonin Gene-Related Peptide.

Nitroxyl (HNO) donors offer considerable therapeutic potential for the treatment of hypertension-related cardiovascular disorders, particularly heart failure, as they combine an inotropic action with peripheral vasodilation. Angeli's salt is the only HNO donor whose mechanism has been studied in depth, and recently, Angeli's salt vasodilation was suggested to be indirect and caused by calcitonin gene-related peptide (CGRP) released from perivascular nerves after HNO activates TRPA1 (transient receptor potential cation channel subfamily A member 1) channels. We investigated resistance artery vasorelaxation to the HNO donor, isopropylamine NONOate (IPA/NO), one of the structures providing a template for therapeutic development. Wire myography in combination with measurements of smooth muscle membrane potential was used to characterize the effect of IPA/NO in mesenteric resistance arteries. Immunohistochemistry was assessed in pressurized arteries. IPA/NO concentration dependently hyperpolarized and relaxed arteries precontracted with the α1-adrenoreceptor agonist, phenylephrine. These effects were blocked by the soluble guanylyl cyclase inhibitor, ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) but not by the KATP channel inhibitor, glibenclamide. Vasorelaxation persisted in the presence of raised [K+]o, used to block hyperpolarization, capsaicin to deplete perivascular CGRP, or HC030031 (2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4 isopropylphenyl) acetamide) to block TRPA1 receptors. Without preconstriction, hyperpolarization to IPA/NO was suppressed by glibenclamide, capsaicin, or HC030031. Hyperpolarization but not vasorelaxation to exogenous CGRP was inhibited with glibenclamide. Thus, vascular hyperpolarization is not necessary for vasorelaxation to the HNO donor IPA/NO, even though both effects are cGMP dependent. The reduced hyperpolarization after depletion of perivascular CGRP or block of TRPA1 receptors indicates some release of CGRP, but this does not contribute to HNO vasorelaxation. Therefore, HNO-TRPA1-CGRP signaling does not seem important for vasodilation to IPA/NO in resistance arteries.

Neurotrophic Effect of Hepatic Growth Factor (HGF) on Reinnervation of Perivascular Calcitonin Gene-Related Peptide (CGRP)-Containing Nerves Following Phenol-Induced Nerve Injury in the Rat Mesenteric Artery

Hepatic growth factor (HGF) has neurotrophic effects in the motor neurons and central nervous system. However, there has been no report about the neurotrophic action on perivascular nerves innervating the resistance artery. We investigated whether HGF can restore innervation or function of perivascular nerves, including neuropeptide Y (NPY)-containing sympathetic adrenergic nerves and calcitonin gene-related peptide (CGRP)-containing nerves, in rat mesenteric artery. To investigate HGF-mediated neurotrophic effects, Wistar rats under pentobarbital-Na anesthesia underwent in vivo perivascular denervation by topical application of phenol on the superior mesenteric artery, and then HGF or nerve growth factor (NGF) was administered for 7 days using an osmotic mini-pump after phenol-treatment. HGF significantly increased the density and number of CGRP-like immunoreactivity (LI)–containing nerve fibers compared with saline administration, while HGF did not affect the density of NPY-containing adrenergic nerve fibers. After 7-day treatment with HGF and phenol, the vascular response of vasodilation was recovered from nerve injury by phenol treatment, but vasoconstriction was not. HGF and NGF induced neurite outgrowth in rat cultured dorsal root ganglia (DRG). These results suggest that HGF has a specific neurotrophic action on reinnervation of vascular CGRP-LI–containing nerve fibers in the rat mesenteric artery and DRG.

Methanandamide Hyperpolarizes Gastric Arteries by Stimulation of TRPV1 Receptors on Perivascular CGRP Containing Nerves

Endogenous as well as synthetic cannabinoids have potent vasodilatory actions in a variety of vascular preparations. Their precise mechanism of action is as yet unclear, but several studies point to the activation of type 1 vanilloid (TRPV1) receptors on primary afferent perivascular nerves, stimulating the release of calcitonin gene related peptide (CGRP). Given the documented gastroprotective function of these nerves, and the various gastrointestinal effects reported for cannabinoids, we explored a possible link between these systems in the gastric circulation by comparing responses of small gastric arteries to cannabinoids and to calcitonin gene related peptide using conventional microelectrode techniques. Exposure of small gastric arteries to the stable endocannabinoid analogue methanandamide caused a hyperpolarization of the vascular smooth muscle cells, which was completely abolished by the vanilloid receptor antagonist capsazepine (P < 0.01). Exposure to exogenous calcitonin gene related peptide evoked fully reproducible (P > 0.05) hyperpolarizations with similar time course, unaffected by capsazepine. Preincubation with glibenclamide, an inhibitor of ATP-sensitive potassium (KATP) channels, reversed both responses to methanandamide (P < 0.01) and calcitonin gene related peptide (P < 0.05). Similar results were found in rat mesenteric arteries. These findings show that cannabinoids stimulate TRPV1 receptors, presumably causing the release of calcitonin gene related peptide, which hyperpolarizes the smooth muscle cells by activation of KATP channels. Because membrane hyperpolarization is a powerful mediator of vasorelaxation, this novel pathway might prove to be an important mechanism affording gastroprotection.

Innervation and functional changes in mesenteric perivascular calcitonin gene-related peptide- and neuropeptide Y-containing nerves following topical phenol treatment

We have previously shown that age-related reduction of innervation and function in mesenteric perivascular calcitonin gene-related peptide-containing vasodilator nerves takes place in spontaneously hypertensive rats. The present study was performed to investigate innervation and functional changes in perivascular calcitonin gene-related peptide- and adrenergic neuropeptide Y-containing nerves after topical treatment with phenol, which damages nerve fibers, around the rat superior mesenteric artery. Under pentobarbital-Na anesthesia, 8-week-old Wistar rats underwent in vivo topical application of phenol (10% phenol in 90% ethanol) or saline (sham rats) to the superior mesenteric artery proximal to the bifurcation of the abdominal aorta. After the treatment, the animals were subjected to immunohistochemistry of the 3rd branch of small arteries proximal to the intestine and to vascular responsiveness testing on day 3 through day 14. The innervation levels of calcitonin gene-related peptide-like immunoreactivity containing fibers and neuropeptide Y-like immunoreactivity containing fibers were markedly reduced on day 3 to day 14 and on day 5 to day 14 after the treatment, compared with those in sham-operated rats, respectively. In perfused mesenteric vascular beds isolated from phenol-treated rats, adrenergic nerve-mediated vasoconstriction and calcitonin gene-related peptide nerve-mediated vasodilation in response to periarterial nerve stimulation (2–12 Hz) were significantly decreased on day 3 and day 7. Neurogenic release of norepinephrine in phenol-treated rats on day 7 was significantly smaller that that in sham-operated rats. Nerve growth factor content in the mesenteric arteries of phenol-treated rats was significantly lower than that in sham-operated rats. Administration of nerve growth factor using osmotic mini-pumps for 7 days after the phenol treatment resulted in greater density of calcitonin gene-related peptide- and neuropeptide Y-like immunoreactivity fibers than in phenol-treated rats and restored decreased vascular responses to periarterial nerve stimulation. These results suggest that topical phenol-treatment of the mesenteric artery effectively induces functional denervation of perivascular nerves, which can be prevented or reversed by nerve growth factor treatment.

CGRP and adrenomedullin receptor populations in human cerebral arteries: in vitro pharmacological and molecular investigations in different artery sizes

The aim of the present study was to determine functional and molecular characteristics of receptors for calcitonin gene-related peptide (CGRP) and adrenomedullin in three different diameter groups of lenticulostriate arteries. Furthermore, the presence of perivascular neuronal sources of CGRP was evaluated in these arteries. In the functional studies, in vitro pharmacological experiments demonstrated that both CGRP and adrenomedullin induce α-CGRP-(8-37) sensitive vasodilation in artery segments of various diameters. The maximal amounts of vasodilation induced by CGRP and adrenomedullin were not different, whereas the potency of CGRP exceeded that of adrenomedullin by 2 orders of magnitude. Significant negative correlations between artery diameters and maximal responses were demonstrated for CGRP and adrenomedullin. In addition, the potency of both peptides tended to increase in decreasing artery diameter. In the molecular experiments, levels of mRNAs encoding CGRP receptors and receptor subunits were compared using reverse transcriptase polymerase chain reactions (RT-PCR). The larger the artery, the more mRNA encoding receptor activity-modifying proteins 1 and 2 (RAMP1 and RAMP2) was detected relative to the amount of mRNA encoding the calcitonin receptor-like receptor. By immunohistochemistry, perivascular CGRP containing nerve fibres were demonstrated in all the investigated artery sizes. In conclusion, both CGRP and adrenomedullin induced vasodilation via CGRP receptors in human lenticulostriate artery of various diameter. The artery responsiveness to the CGRP receptor agonists increased with smaller artery diameter, whereas the receptor-phenotype determining mRNA ratios tended to decrease. No evidence for CGRP and adrenomedullin receptor heterogeneity was present in lenticulostriate arteries of different diameters.

Endogenous calcitonin gene-related peptide suppresses vasoconstriction mediated by adrenergic nerves in rat mesenteric resistance blood vessels

The role of perivascular calcitonin gene-related peptide (CGRP)-containing nerves in the modulation of adrenergic nerve-mediated vasoconstrictions was studied in the rat perfused mesenteric vascular bed. A frequency-dependent vasoconstriction induced by periarterial nerve stimulation (1–6 Hz) of the bed was significantly potentiated by perfusion of 1 μM CGRP-(8–37) (CGRP receptor antagonist) or to a similar extent after treatment with 500 nM capsaicin. In the preparations treated with capsaicin, CGRP-(8–37) caused a small potentiation of periarterial nerve stimulation-induced vasoconstriction. Exogenous CGRP (0.1–1 nM) concentration-dependently attenuated the augmented vasoconstriction in response to periarterial nerve stimulation after treatment with capsaicin. However, exogenous CGRP (1 nM) did not attenuate the periarterial nerve stimulation-induced vasoconstriction in the bed untreated with capsaicin. These results suggest that endogenous CGRP, which is released from CGRP-containing nerves, suppresses the adrenergic nerve function involved in mechanisms regulating the tone of resistant blood vessels.

Calcitonin gene-related peptide (human α-CGRP) counteracts vasoconstriction in human subarachnoid haemorrhage

Calcitonin gene-related peptide (CGRP) is a neuropeptide co-stored with tachykinins (substance P, neurokinin A) in cerebrovascular sensory fibers in the trigeminal ganglion. Preceding studies on subarachnoid hemorrhage (SAH) revealed that an enhanced release of CGRP resulted in the selective loss of perivascular CGRP. Therefore, the present study was designed to evaluate the effects of intravenous administration of human α-CGRP on cerebral vasoconstriction in the postoperative course after SAH in 5 patients (8 infusions). Cerebral vasoconstriction was evaluated with transcranial Doppler sonography. The increase in the relationship between middle cerebral artery (MCA) velocity and internal carotid artery (ICA) velocity (the hemodynamic index) was used as an indicator of vasoconstriction and compared to the contralateral side. A significant reduction was found in the hemodynamic index during the CGRP infusion (4.3 ± 0.5, P < 0.05) as to compared to before infusion (6.2 ± 0.5). There was no measurable change in the hemodynamic index on the contralateral side. No significant change was observed in pulsatility index, blood pressure or consciousness during the peptide infusion. A significant increase in heart rate was observed during the infusion as compared to before and after infusion (90 ± 4 vs. 76 ± 5). Cardiac ultrasound data indicated a mean cardiac output increase of 1.9 liter/min, and a mean decrease in total peripheral resistance of 538 dynes s/cm 5. The results obtained show that infusion of human α-CGRP may induce normalisation of cerebrovascular tone in SAH.

Calcitonin gene-related peptide (CGRP): perivascular distribution and vasodilatory effects

The distribution of perivascular nerve fibers displaying calcitonin gene-related peptide (CGRP) immunoreactivity and the effect of CGRP on vascular smooth muscle were studied in the guinea-pig. Perivascular CGRP fibers were seen in all vascular beds. Generally, they were more numerous around arteries than veins. Small arteries in the respiratory tract, gastrointestinal tract and genitourinary tract had numerous CGRP fibers. The gastroepiploic artery in particular received a rich supply of such fibers. Coronary blood vessels had a moderate supply of CGRP fibers. In the heart, a moderate number of CGRP fibers was seen running close to myocardial fibers. The atria had a richer supply than the ventricles. Numerous CGRP immunoreactive nerve cell bodies and nerve fibers were seen in sensory (trigeminal, jugular and spinal dorsal root) ganglia. Sequential or double immunostaining with antibodies against substance P and CGRP suggested co-existence of the two peptides in nerve cell bodies in the ganglia and in perivascular fibers. In agreement with previous findings CGRP turned out to be a strong vasodilator in vitro as tested on several blood vessels (e.g. basilar, gastroepiploic and mesenteric arteries). Conceivably, perivascular CGRP/SP fibers have a dual role as regulator of local blood flow and as carrier of sensory information.