Calcitonin Gene-related Peptide Concentrations Research Articles

Contribution of Sensory Neurons to Sex Difference in the Development of Stress-Induced Gastric Mucosal Injury in Mice

Sensory neurons play a critical role in reducing stress-induced gastric mucosal injury by releasing calcitonin gene-related peptide (CGRP) through an increase in gastric mucosal levels of prostacyclin (PGI(2)). Because estrogen enhances nerve growth factor-mediated CGRP production in sensory neurons, we hypothesized that stress-induced gastric mucosal injury occurs less in females than in males. Gastric ulcer index, gastric myeloperoxidase activity, and gastric tissue levels of CGRP and 6-keto-PGF(1alpha), a stable metabolite of PGI(2), were determined in male and female wild-type (CGRP(+/+)) mice and CGRP knockout (CGRP(-/-)) mice subjected to water-immersion restraint stress. In CGRP(+/+) mice, ulcer index and myeloperoxidase activities were lower and gastric tissue levels of CGRP and 6-keto-PGF(1alpha) were higher in female mice than in male mice, but there were no such sex differences in CGRP(-/-)mice. Sex differences in CGRP(+/+) mice were eliminated by pretreatment with SB366791 (500 microg/kg intraperitoneally), a vanilloid receptor antagonist, and by ovariectomy. Reversal of sex differences by ovariectomy was not observed in female CGRP(+/+) mice with estradiol replacement (1 mg . kg(-1). wk(-1) for 3 weeks). Levels of CGRP messenger RNA in dorsal root ganglion neurons isolated from female CGRP(+/+) mice were decreased by ovariectomy, and these decreases were reversed by estradiol replacement. Estrogen-mediated increases in CGRP levels in sensory neurons might contribute to reduce stress-induced gastric mucosal injury by attenuating inflammatory responses. This might at least partly explain the sex difference observed in the development of stress-induced gastric mucosal injury in mice.

Clinicopharmacological Study of Gastrointestinal Drugs from the Viewpoint of Postmarketing Development

Pharmaceutical development starts with the discovery of a new compound. Drugs become commercially available after non-clinical and clinical studies, but processes that take place after marketing are also important for pharmaceutical development. In recent years, use of the phrase "Ikuyaku" meaning postmarketing development has become more common. Sometimes, the proper usage, indications and harmful effects of a drug are discovered only after it becomes commercially available and is administered to many patients. Hence, pharmacists need to actively perform postmarketing studies to reveal the true nature of drugs. In the present clinicopharmacological study, we investigated the effects of histamine H(2) receptor antagonists (H(2)-RAs) on the plasma concentrations of gastrointestinal peptides from the viewpoint of postmarketing development. First we established an enzyme immunoassay for secretin, which is involved in gastrointestinal motility. Then we used this and existing peptide assays to investigate the above-mentioned issues. Ranitidine and nizatidine increased the plasma concentration of motilin. It is believed that the plasma concentration of Ach is elevated by ranitidine and nizatidine, which possesses an anti-AchE activity, and that the increased the plasma concentration of Ach facilitated release of motilin, elevating the plasma concentration of motilin. When compared to the placebo, lafutidine significantly increased the plasma concentration of CGRP (calcitonin gene-related peptide) and substance P. Furthermore, released CGRP stimulated CGRP1 receptors to facilitate secretion of somatostatin. Therefore, lafutidine appears to protect the gastric mucosa and regulate gastrointestinal motility. The same results were obtained with ranitidine and nizatidine. While H(2)-RAs have a common function in suppressing the secretion of gastric acid, they do not exhibit the same effects on factors related to recurrence of peptic ulcer, such as gastrointestinal motility and blood flow in the gastrointestinal mucosa. Hence, measuring the plasma concentration of gastrointestinal peptides can be used to estimate the effects of drugs on gastrointestinal motility. From the viewpoint of postmarketing development, we are in the process of establishing indicators for the proper usage of pharmaceutical drugs. Pharmacists need to closely follow and monitor adverse reactions. In order to further improve monitoring of drug therapy, it will be necessary to assess not only the blood concentrations of drugs, but also biological reactions to the drugs. Since the levels of peptides reflect the clinical efficacy of gastrointestinal drugs, measuring peptide levels appears to be useful for selecting appropriate drugs.

Clonidine inhibits the canine external carotid vasodilatation to capsaicin by α2A/2C-adrenoceptors

Migraine is a disorder associated with increased plasma concentrations of calcitonin gene-related peptide (CGRP). CGRP, a neuropeptide released from activated trigeminal sensory nerves, dilates cranial blood vessels and transmits vascular nociception. Moreover, several antimigraine drugs inhibit the dural neurogenic vasodilatation to trigeminal stimulation. Hence, this study investigated in anaesthetized dogs the effects of the α 2-adrenoceptor agonist, clonidine, on the external carotid vasodilator responses to capsaicin, α-CGRP and acetylcholine. 1-min intracarotid infusions of capsaicin (10, 18, 30 and 56 μg/min), α-CGRP (0.1, 0.3, 1 and 3 μg/min) and acetylcholine (0.01, 0.03, 0.1 and 0.3 μg/min) produced dose-dependent increases in external carotid conductance without affecting blood pressure or heart rate. Interestingly, the carotid vasodilator responses to capsaicin, but not those to α-CGRP or acetylcholine, were partially inhibited after clonidine (total dose: 24.4 μg/kg, i.v.); in contrast, equivalent volumes of saline did not affect the responses to capsaicin, α-CGRP or acetylcholine. The inhibitory responses to clonidine were antagonized by i.v. administration of the α 2-adrenoceptor antagonists rauwolscine ( α 2A/2B/2C; 300 μg/kg), BRL44408 ( α 2A; 1000 μg/kg) or MK912 ( α 2C; 100 and 300 μg/kg), but not by imiloxan ( α 2B; 1000 μg/kg). These results suggest that clonidine inhibits the external carotid vasodilator responses to capsaicin by peripheral trigeminovascular and/or central mechanisms; this inhibitory response to clonidine seems to be predominantly mediated by α 2A-adrenoceptors and, to a much lesser extent, by α 2C-adrenoceptors.

Bone and bone related biochemical examinations. Hormone and hormone related substances. Calcitonin gene-related peptide (CGRP)

Calcitonin gene-related peptide (CGRP) is secreted from osteoclasts and several cancer cells, as well as from sensory nerve endings innervating blood vessels and bones. A potent vasodilator, CGRP powerfully counteracts hypertensive responses and protects organs from blood pressure-related damage, though it also can precipitate migraine attacks, bronchoconstriction and hypersensitive colon. Because plasma CGRP concentrations are very low, even in patients, it is thought that CGRP functions as local modulator rather than as a circulating hormone. Nevertheless, it is useful to measure plasma CGRP when evaluating the severity of target diseases (e.g., heart failure and sepsis) and when screening or following up patients with neuroendocrine tumors (e.g., medullary thyroid carcinoma). That said, one should understand the biochemical characteristics of CGRP prior to blood sampling, and should use highly sensitive assays that detect only the active form of the molecule.

Release of calcitonin gene-related peptide from the isolated mouse heart: Methodological validation of a new model

Calcitonin gene-related peptide (CGRP), a potent vasodilator released from a subset of sensory Adelta- and C-fiber afferents, has been suggested to play a beneficial role in myocardial ischemia. Variations in CGRP release can possibly be correlated with diseases that involve changes in activity or degeneration of cardial afferent fibers. The aim of the present study was to evaluate a simple and easily reproducible model for measuring stimulated CGRP release from cardial afferents. For this reason freshly isolated mouse hearts were passed through incubations in series of 25 min. Solutions consisting of oxygenated synthetic interstitial fluid. Dissolved substances such as capsaicin, bradykinin and potassium chloride were used as excitatory test stimuli. For comparison, isolated mouse hearts were perfused with the same solutions through a cannula inserted into the rising aorta. The eluates were processed using an enzyme immuno-assay for measurement of CGRP concentrations. Capsaicin, bradykinin and the potassium solution caused concentration-dependent increases in CGRP release. There were no differences in CGRP release when oxygen was replaced by nitrogen in the solutions. Immersion of hearts caused significantly more CGRP release than perfusion with same solutions. The results suggest that mouse heart immersion is more effective than coronary perfusion in measuring stimulated CGRP release from cardial afferents which are widely distributed in the epicardium but rare in deeper myocardial layers. The results are discussed with respect to the potentially important vasodilatory and cardioprotective functions of CGRP released from activated epicardial afferents.

A study of neuropeptides related to headaches in children with meningeal irritation signs

Purpose : The headache, one of the symptoms of meningitis, is related to abrupt elevation of intracranial pressure(ICP) or stimulation of intracranial nociceptive structure. However, in cases of mild elevation of ICP or normal findings of cerebrospinal fluid(CSF) analysis, patients sometimes complain of headaches. Therefore, other pathways may contribute to the occurrence of headaches in aseptic meningitis or meningismus. We intend to investigate the role of substance P(SP) and calcitonin gene-related peptide(CGRP) in aseptic meningitis or meningismus. Methods : We measured leukocyte count, the concentration of protein and glucose in CSF and ICP of patients with meningeal irritation sign. We also measured SP and CGRP levels by using immunoassay. We analyzed the relationship between the presence of headache and the value of SP and CGRP. Results : The concentrations of CGRP(18.8±10.5 ng/mL) in CSF and ICP(14.8±4.5 cmH2O) in aseptic meningitis group were significantly higher than in those(14.1±7.4 ng/mL and 12.0±5.1 cmH2O, respectively) of the meningismus group(P<0.05). There was no significant difference in the SP levels between the two groups. In the aseptic meningitis group, the concentrations of SP and CGRP were significantly higher in the normal ICP group than in the elevated ICP group(P<0.05). Conclusion : Headaches in children with aseptic meningitis or meningismus is considered to be related to the elevation of the CSF levels of SP and CGRP. (Korean J Pediatr 2006;49:533-538)

Lafutidine, a Newly Developed Antiulcer Drug, Elevates Postprandial Intragastric pH and Increases Plasma Calcitonin Gene-Related Peptide and Somatostatin Concentrations in Humans: Comparisons with Famotidine

Lafutidine, a newly developed histamine H(2)-receptor antagonist, inhibits daytime (i.e., postprandial) as well as nighttime gastric acid secretion in clinical studies. It also has gastroprotective activity that particularly affects mucosal blood flow in rats. This study focused on the efficacy of lafutidine on plasma concentrations of gastrointestinal peptides in humans. Six healthy male volunteers aged 23-32 years without Helicobacter pylori infection were orally administered either 10 mg lafutidine, 20 mg famotidine, or water only (control) 30 min after a standard meal (650 kcal). Plasma concentrations of lafutidine and famotidine were highest from 90 to 150 min after administration. Intragastric pH was elevated after both lafutidine and famotidine compared with the control. Plasma concentrations of calcitonin gene-related peptide (CGRP) and somatostatin were significantly increased after lafutidine at 60 and 90 min. We concluded that lafutidine increases plasma concentrations of CGRP and somatostatin in humans, which may result in inhibition of postprandial acid secretion and gastroprotective activity.

Lack of Effect of the Adenosine A1 Receptor Agonist, GR79236, on Capsaicin-Induced CGRP Release in Anaesthetized Pigs

Migraine is a common neurological disorder that is associated with an increase in plasma calcitonin gene-related peptide (CGRP) levels. CGRP, a potent vasodilator released from the activated trigeminal sensory nerves, dilates intracranial blood vessels and transmits vascular nociception. Hence, inhibition of trigeminal CGRP release may prevent neurotransmission and, thereby, ameliorate migraine headache. Therefore, the present study in anaesthetized pigs investigates the effects of a selective adenosine A(1) receptor agonist, GR79236 (3, 10 and 30 microg/kg, i.v.) on capsaicin-induced carotid haemodynamic changes and on plasma CGRP release. Intracarotid (i.c.) infusion of capsaicin (10 microg/kg/min, i.c.) increased the total carotid blood flow and conductance as well as carotid pulsations, but decreased the difference between arterial and jugular venous oxygen saturations. These responses to capsaicin were dose-dependently attenuated by GR79236. However, the increases in the plasma CGRP concentrations by capsaicin remained essentially unmodified after GR79236 treatment. The above results suggest that GR79236 may have an antimigraine potential due to its postjunctional effects (carotid vasoconstriction) rather than to prejunctional inhibition of trigeminal CGRP release.

Calcitonin Gene-Related Peptide during Sweating in Young Healthy Women

Calcitonin gene-related peptide (CGRP) concentrations are increased in postmenopausal women and castrated men with symptomatic flushing. We wanted to determine if a CGRP increase exists in the plasma of healthy fertile-age women during sweating. Plasma concentrations of CGRP were measured by radioimmunoassay at maximal sweating during a sauna session and during bicycle exercise both at maximal and 70% of maximal work capacity in 8 healthy women of fertile age. Plasma concentrations of CGRP were unaffected (>90% statistical power) during both experimental sessions. We suggest that sweating itself does not explain the rise in CGRP concentrations observed in flushing postmenopausal women.

Effects and Mechanism of Changes of Local Neurotransmitters in Rats' Pylorus and Bile Reflux to the Stomach with Stress Ulcer

Stress ulcer occurs primarily in severe conditions, with a high incidence and mortality in intensive care units. However, studies on the association between stress ulcer and bile reflux to the stomach with stress ulcer are still inconclusive. Therefore, our research aimed to determine whether or not bile reflux exists during stress ulcer and then to investigate the effects and mechanism of changes of pyloric local neurotransmitters on bile reflux in such circumstances so as to provide a new pathway for clinical intervention. Cold water immersion was used to copy the stress ulcer model of rats. Sixty-five adult Sprague-Dawley rats of either sex were randomly divided into three groups: the normal control group (n = 10), the stress group (n = 30), and the antagonist group (n = 25). The gastric ulcer index, pH, and bile acid of gastric juice were measured before and after stress. Radio Immunoassay Detection Kit and Biochemic Detection Kit were used to measure local contents of CGRP (calcitonin gene-related peptide) and nitric oxide, respectively, in rats' pylorus. The local contents of nitric oxide in rats' pylorus reached a maximum at 1 hr after stress. The bile acid and pH of gastric juice peaked at 2 hr after stress and the ulcer index peaked at 4 hr after stress. But the local contents of CGRP in rats' pylorus decreased to the minimum at 4 hr after stress. The bile acid and ulcer index in the L-NAME group were significantly lower than in the antagonist control group. However, the bile acid in the hCGRP8-37 group was less than in the antagonist control group. Compared with hCGRP8-37 group, there was a significant reduction in bile acid in the L-NAME group. There was a significant reduction in the ulcer index of the hCGRP8-37 group compared with the L-NAME group and the antagonist control group. There was a certain kind of positive correlation between nitric oxide in rats' pylorus and bile acid to the stomach, for nitric oxide could loosen the pyloric sphincter and increase the bile acid to the stomach. L-NAME might reduce the local nitric oxide contents in rats' pylorus so that bile acid to the stomach might be decreased, obviously with a looser tight pyloric sphincter. Meanwhile, the CGRP in rats' pylorus was negatively associated with the ulcer index, hence CGRP might protect gastric mucosa under stress conditions.

Molecular and functional characterization of adrenomedullin receptors in pufferfish

The receptors for the calcitonin gene-related peptide (CGRP)/adrenomedullin (AM) family peptides were characterized in the mefugu Takifugu obscurus, a euryhaline fugu species very close to Takifugu rubripes, which has as many as five adrenomedullin genes (AM1-5). CGRP and AM share a G protein-coupled core receptor called calcitonin receptor-like receptor (CLR), and the specificity of the CLR is determined by the interaction with receptor activity-modifying proteins (RAMPs). Through database mining, three CLRs (CLR1-3) and five RAMPs (RAMP1-5) were identified, and all of them were cloned by RT-PCR and characterized by functional expression in COS7 cells in every possible combination of CLR-RAMP. The following combinations generated cAMP in response to physiological concentrations of CGRP, AM1 (an ortholog of mammalian AM), AM2, and AM5: CLR1-RAMP1/4 (CGRP), CLR1-RAMP2/3/5 (AM1), CLR2-RAMP2 (AM1), CLR1-RAMP3 (AM2), and CLR1-RAMP3 (AM5). Their expressions were found by Northern blot analysis to be tissue specific and salinity dependent. For example, CLR1-RAMP5 and CLR1-RAMP2 are expressed specifically in the gill and kidney, respectively, suggesting their involvement in osmoregulation. Furthermore, relatively high levels of CLRs and RAMPs were found in the spleen and ovary, suggesting roles in the immune and female reproductive systems. Immunohistochemistry revealed that AM receptors of the following types are expressed in the locations, indicated in brackets, of the mefugu gill and kidney: CLR1-RAMP5 (interlamellar vessels), CLR2-RAMP2 (pillar cells), and CLR1-RAMP2 (apical side of renal proximal tubule cells).

No increase of calcitonin gene–related peptide in jugular blood during migraine

Increased calcitonin gene-related peptide (CGRP) in external jugular venous blood during migraine attack is one of the most cited findings in the headache literature. The finding has not been convincingly reproduced and is based on comparison with historic control subjects. The validity of this finding is important for the understanding of migraine. We therefore investigated the issue using an intrapatient comparison design and two different CGRP assays. We sampled blood from the external jugular and cubital vein during, as well as outside of, an attack of migraine without aura. We succeeded in 17 patients, whereas only cubital fossa blood could be sampled in an additional 4 patients. CGRP was measured with the same assay as most previous studies (assay I) and furthermore with a more sensitive and validated assay (assay II). For assay I, mean CGRP concentration in external jugular venous blood during attack was 17.18 pmol/L compared with 15.88 pmol/L outside of attack. Mean difference was 1.81 pmol/L (95% confidence interval [CI]: -2.88, 6.41; p = 0.44). In peripheral blood during attack, CGRP was 16.86 pmol/L compared with 17.57 pmol/L outside of attack. Mean difference was -0.79 pmol/L (95% CI: -4.64, 3.06; p = 0.69). For assay II, external jugular venous blood concentration of CGRP during attack was 32.59 pmol/L compared with 30.59 pmol/L outside of attack; mean difference was 2.00 pmol/L (standard error, 2.39; 95% CI: -3.07, 7.07; p = 0.416). In peripheral blood during attack, CGRP was 33.37 pmol/L compared with 31.84 pmol/L outside of attack; mean difference was 1.53 pmol/L (standard error, 1.90; 95% CI: -2.46, 5.51; p = 0.431). Thus, no difference between CGRP level in external jugular or cubital fossa blood during and outside of attack was found. No difference was found between external jugular and peripheral venous blood. Thus, previous findings of increased CGRP level in external jugular or cubital fossa venous blood could not be confirmed. Our finding strongly suggests that CGRP is not increased in jugular venous blood during migraine without aura. CGRP cannot be used as a biomarker to validate human or animal models of migraine.

Changes of the neuropeptides content and gene expression in spinal cord and dorsal root ganglion after noxious colorectal distension

Visceral pain/hypersensitivity is a cardinal symptom of functional gastrointestinal disorders. With their peripheral and central (spinal) projections, sensory neurons in the dorsal root ganglia (DRG) are the “gateway” for painful signals emanating from both somatic and visceral structures. In contrast to somatic pain, the neurochemical pathways involved in visceral pain/hypersensitivity have not been well studied. We hypothesized the neuropeptide changes in spinal cord and DRG during visceral pain would mirror similar changes in somatic nociception. Noxious (painful) colorectal distension (CRD) was done by distending a rectal balloon up to 60 mm Hg phasically for 1 h in Sprague–Dawley rats. The spinal content of calcitonin gene-related peptide (CGRP), substance P (SP), galanin and vasoactive intestinal peptide (VIP) as well as their mRNAs in DRG were measured at 0, 4 and 24 h after the CRD. Visceromotor reflex (VMR) was measured by recording the electromyogram at the abdominal muscle in response to CRD. Distal colorectum was removed for evaluating the presence of inflammation. No significant evidence of histological inflammation was seen in the colonic mucosa/submucosa after repeated CRD, which is confirmed by myeloperoxidase assay. The spinal content of CGRP and SP decreased significantly 4 h after CRD, while galanin and VIP levels increased gradually and reached highest level at 24 h ( p < 0.05). The mRNAs in DRG of the neuropeptides were significantly upregulated after CRD ( p < 0.05). VMR recording showed the rat's colon became hypersensitive 4 h after CRD, a sequence parallel to the spinal changes of CGRP and SP in timeframe. Noxious mechanical distension of the colorectum causes an acute change in the spinal levels of excitatory neurotransmitters (CGRP and SP), probably reflecting central release of these peptides from sensory neurons and contributing to the hypersensitivity following the noxious CRD. This is followed by a slower change in the levels of the inhibitory neurotransmitter galanin and VIP. Such stimulation results in significant alternation of the gene expression in DRG, reflecting the plasticity of the neuronal response. In the absence of visceral inflammation, the aforementioned neuropeptides are important mediators in the processing of visceral pain/hypersensitivity.

Strong relationships between mediators of the acute phase response and fatty liver in dairy cows

The objective of this study was to investigate the relationship between activation of acute phase response and fatty liver in transition dairy cows. Fatty liver was induced in dairy cows by feeding 8 kg of cracked corn 1 mo before the expected day of parturition. Liver and blood samples were obtained at days -4, 3, 8, 12, 14, 22, 27, and 36 postpartum. Cows that developed fatty liver (n = 4) reached peak total lipids in the liver at day 12 postpartum with 11.4% (wet wt.) compared with 6.6% in control cows (n = 4). Cows with fatty liver had greater plasma tumor necrosis factor-alpha (TNF-α), nonesterified fatty acids (NEFA), and lower lactate concentrations than did control cows at day -4. During highest concentrations of total lipids in the liver, for at least one time-point, fatty-liver cows had greater concentrations of plasma serum amyloid A (SAA), haptoglobin, and NEFA and lower concentrations of calcitonin gene-related peptide (CGRP), prostaglandin E2 (PGE2), cortisol, and TNF-α than did control cows. Concentrations of total lipids in the liver at 12 d postpartum were correlated (a) positively with plasma TNF-α, SAA, and NEFA and negatively with plasma CGRP before calving, (b) positively with plasma SAA, haptoglobin, and NEFA and negatively with plasma PGE2, CGRP, total cholesterol, and glucose at days 3, 8, and 12 postpartum, and (c) negatively with concentrations of plasma glucose, lactate, and total bilirubin after day 12 postpartum. In conclusion, this study indicates that the acute phase response occurs in cows with fatty liver as well as strong relationships between mediators of immune response and fatty liver. Key words: Acute phase response, fatty liver, dairy cow

The Protective Effects of Rutaecarpine on Gastric Mucosa Injury in Rats

Previous investigations have shown that calcitonin gene-related peptide (CGRP) protects gastric mucosa against injury induced by acetylsalicylic acid (ASA) and that rutaecarpine activates vanilloid receptors to evoke CGRP release. In the present study, we examined the protective effects of rutaecarpine on gastric mucosa injury, and explored whether the protective effects of rutaecarpine are related to stimulation of endogenous CGRP release via activating vanilloid receptors in rats. In an ASA-induced ulceration model, gastric mucosal ulcer index, pH value of gastric juice and plasma concentrations of CGRP were determined. ASA significantly increased the gastric mucosal ulcer index and the back-diffusion of H+ through the mucosa. Rutaecarpine at the doses of 100 or 300 microg/kg (i.v.), and 300 or 600 microg/kg (intragastric, i.g.) reduced the ulcer index and back-diffusion of H+, which was abolished by pretreatment with capsaicin (50 mg/kg, s.c.) or capsazepine (3 mg/kg, i.v.), a competitive vanilloid receptor antagonist. Rutaecarpine significantly increased the plasma concentration of CGRP, which was also abolished by capsazepine. In a stress-induced ulceration model, rutaecarpine reduced gastric mucosal damages, which was abolished by capsazepine (5 mg/kg, i.p.). These results suggest that rutaecarpine protects the gastric mucosa against injury induced by ASA and stress, and that the gastroprotective effect of rutaecarpine is related to a stimulation of endogenous CGRP release via activation of the vanilloid receptor.

Gastric Perception Thresholds Are Low and Sensory Neuropeptide Levels High in Helicobacter pylori-Positive Functional Dyspepsia

Background and Aims: In functional dyspepsia (FD) decreased perception levels can be shown on gastric distension. Substance P (SP) and calcitonin gene-related peptide (CGRP) are involved in the sensitization of afferent neuronal pathways due to chronic inflammation. The role of Helicobacter pylori-induced gastric mucosal inflammation in the pathogenesis of FD is controversial. The aim of this study was to assess whether FD patients have altered mucosal concentrations of CGRP and SP, and to investigate whether this is associated with visceral hypersensitivity or H. pylori infection. Methods: Gastrointestinal symptoms, H. pylori status, perception thresholds at gastric balloon distension, and gastric mucosal concentrations of CGRP and SP were determined in 13 FD patients and 18 healthy controls (HC). Results: In H. pylori-positive FD patients discomfort and pain thresholds on gastric distension were lower compared to other groups. Antral mucosal levels of CGRP and SP were higher in H. pylori-positive subjects. In FD significantly negative correlations between discomfort and pain thresholds and antral mucosal concentrations of CGRP and SP were observed. Conclusions: In FD low perception thresholds on gastric distension are associated with high levels of CGRP and SP in the antrum, suggesting that sensory neuropeptides are involved in FD pathophysiology.

The effect of endoneurial nerve growth factor on calcitonin gene-related peptide expression in primary sensory neurons

Recent findings indicate that calcitonin gene-related peptide (CGRP) is involved in neuropathic pain, this peptide being up-regulated in a small population of large- and medium-sized primary sensory neurons after peripheral nerve injury. In adult animals, the expression of CGRP is regulated by nerve growth factor (NGF). After nerve injury, NGF is up-regulated at the injury site for several weeks, and this up-regulation contributes to the onset of neuropathic pain. Using immunohistochemistry, we investigated the time course of the effect of an endoneurial injection of NGF on the expression of CGRP in primary sensory neurons. NGF increased the percentage of medium- to large-sized DRG neuron profiles expressing CGRP, did not modify the percentage of small-sized neurons expressing CGRP, and increased CGRP expression in the laminae III and IV of the dorsal horn. The effects of NGF were evident as soon as 1 day after endoneurial injection, and lasted for 5 days. Ten days after the injection of NGF, the patterns of CGRP expression in the DRG were normal, whereas a slight decrease in CGRP content was observed in the dorsal horn. The injection of vehicle did not produce any change on CGRP expression in primary sensory neurons. These results suggest that endoneurial NGF is responsible for the increase in CGRP expression in some large-sized neurons and their central processes observed after nerve injury in animal models of neuropathic pain. Our findings contribute to the understanding of the role of NGF in neuropathic pain.

Study of Innervation, Sensory Neuropeptides, and Serotonin in Murine Contact Allergic Skin

Density of nerve fibers, axonal growth, calcitonin gene-related peptide (CGRP), and substance P, and serotonin immunoreactivity as well as concentration were all determined in a murine model of contact allergy. Female Balb/c mice were sensitized on the back with oxazolone and 6 days later challenged with the same antigen on the dorsal surface of the ears, while control mice received the vehicle only. Then, 24 hr postchallenge, one ear was processed for immunohistochemical staining, while the other was frozen and processed for gas chromatography-mass spectrometry or radioimmunoassay (RIA). Protein gene product 9.5 (PGP 9.5) positive nerve fibers showed a tendency to increase in inflamed ears versus control ears in epidermis as well as the dermis. Growth-associated protein-43 (GAP-43) positive fibers in the epidermis were increased (p < .01) in inflamed ears, compared with control ears, as was the case for the dermal fibers, indicating increased axonal growth. Total (epidermis and dermis) numbers of CGRP and substance P positive nerve fibers tended to increase in the inflamed skin in contrast to control skin. In contrast, RIA demonstrated a lower(p < .05) concentration of CGRP in the inflamed ears compared with controls and a tendency for substance P to decrease in concentration in eczematous ears versus controls. There was no difference in serotonin concentration, or in the number of serotonin positive mast cells, between the inflamed and control skin, whereas semiquantification of serotonin positive platelets showed an increase in the inflamed (++) compared with control ears (+). Our results indicate that 24 hr after being challenged with the antigen, at the peak of murine skin inflammation, axonal growth, sensory neuropeptides, as well as serotonin may be involved.

Sumatriptan Causes Parallel Decrease in Plasma Calcitonin Gene-Related Peptide (CGRP) Concentration and Migraine Headache During Nitroglycerin Induced Migraine Attack

Sumatriptan-induced changes in plasma calcitonin gene-related peptide (CGRP) concentration and headache intensity were investigated in 19 female migraineurs during nitroglycerin-induced migraine attack. Sumatriptan nasal spray was administered 120 min after the onset of the attack. Blood samples were obtained immediately before and 60 min after sumatriptan administration. In those subjects whose migraine attack improved considerably 60 min after the treatment the plasma CGRP concentration decreased significantly (P<0.05). In contrast, plasma CGRP concentration failed to change in patients whose headache did not improve. In addition, plasma CGRP concentrations showed significant positive correlations with the headache scores both 60 and 120 min after sumatriptan administration (P<0.05). According to our results plasma CGRP concentration decreases parallel to headache intensity during sumatriptan treatment and this decrease in CGRP predicts effectiveness of antimigraine drug therapy. This supports that one of the main effects of triptans is to decrease CGRP release.

Interactions of sympathetic nerves with capsaicin-sensitive sensory nerves: neurogenic mechanisms for phenol-induced hypertension in the rat

Previous investigations have shown that norepinephrine is capable of inhibiting neurotransmission in capsaicin-sensitive sensory nerves via a prejunctional mechanism. The alteration in the activity of sympathetic or capsaicin-sensitive sensory nerves in the development of phenol-induced hypertension was observed separately in rats. In the present study, we examined interactions of adrenergic nerves with capsaicin-sensitive sensory nerves in phenol-induced hypertensive rats. Blood pressure, the synthesis and release of calcitonin gene-related peptide (CGRP) and the content of nerve growth factor in (NGF) arteries were determined. Intrarenal injection of phenol caused a permanent elevation of blood pressure concomitantly with a decrease in the concentration of CGRP in plasma, the content of CGRP in dorsal root ganglia and the density of CGRP-containing nerves in the mesenteric artery, and vascular NGF content. Chronic treatment with prazosin (an alpha1-adrenoreceptor antagonist, 3 mg/kg per day) failed to alter the synthesis and release of CGRP and vascular NGF content, even though it completely normalized blood pressure. However, treatment with yohimbine (an alpha2-adrenoreceptor antagonist, 5 mg/kg per day) significantly increased CGRP level and vascular NGF content. Combined administration of prazosin and yohimbine not only significantly elevated the synthesis and release of CGRP and arterial NGF content, but also completely normalized blood pressure. These results indicate that the decreased production and release of CGRP and reduced vascular NGF content are attributed to the activation of alpha2-adrenoreceptors in phenol-induced hypertensive rats.