Amount Of Calcitonin Gene-related Peptide Research Articles

Sensory nerves drive migration of dental pulp stem cells via the CGRP-Ramp1 axis in pulp repair

Dental pulp stem cells (DPSCs) are responsible for maintaining pulp structure and function after pulp injury. DPSCs migrate directionally to the injury site before differentiating into odontoblast-like cells, which is a prerequisite and a determinant in pulp repair. Increasing evidence suggests that sensory neuron-stem cell crosstalk is critical for maintaining normal physiological functions, and sensory nerves influence stem cells mainly by neuropeptides. However, the role of sensory nerves on DPSC behaviors after pulp injury is largely unexplored. Here, we find that sensory nerves released significant amounts of calcitonin gene-related peptide (CGRP) near the injury site, acting directly on DPSCs via receptor activity modifying protein 1 (RAMP1) to promote collective migration of DPSCs to the injury site, and ultimately promoting pulp repair. Specifically, sensory denervation leads to poor pulp repair and ectopic mineralization, in parallel with that DPSCs failed to be recruited to the injury site. Furthermore, in vitro evidence shows that sensory nerve-deficient microenvironment suppressed DPSC migration prominently among all related behaviors. Mechanistically, the CGRP-Ramp1 axis between sensory neurons and DPSCs was screened by single-cell RNA-seq analysis and immunohistochemical studies confirmed that the expression of CGRP rather than Ramp1 increases substantially near the damaged site. We further demonstrated that CGRP released by sensory nerves binds the receptor Ramp1 on DPSCs to facilitate cell collective migration by an indirect co-culture system using conditioned medium from trigeminal neurons, CGRP recombinant protein and antagonists BIBN4096. The treatment with exogenous CGRP promoted the recruitment of DPSCs, and ultimately enhanced the quality of pulp repair. Targeting the sensory nerve could therefore provide a new strategy for stem cell-based pulp repair and regeneration.

Electro-acupuncture and its combination with adult stem cell transplantation for spinal cord injury treatment: A summary of current laboratory findings and a review of literature.

The incidence and disability rate of spinal cord injury (SCI) worldwide are high, imposing a heavy burden on patients. Considerable research efforts have been directed toward identifying new strategies to effectively treat SCI. Governor Vessel electro‐acupuncture (GV‐EA), used in traditional Chinese medicine, combines acupuncture with modern electrical stimulation. It has been shown to improve the microenvironment of injured spinal cord (SC) by increasing levels of endogenous neurotrophic factors and reducing inflammation, thereby protecting injured neurons and promoting myelination. In addition, axons extending from transplanted stem cell‐derived neurons can potentially bridge the two severed ends of tissues in a transected SC to rebuild neuronal circuits and restore motor and sensory functions. However, every single treatment approach to severe SCI has proven unsatisfactory. Combining different treatments—for example, electro‐acupuncture (EA) with adult stem cell transplantation—appears to be a more promising strategy. In this review, we have summarized the recent progress over the past two decades by our team especially in the use of GV‐EA for the repair of SCI. By this strategy, we have shown that EA can stimulate the nerve endings of the meningeal branch. This would elicit the dorsal root ganglion neurons to secrete excess amounts of calcitonin gene‐related peptide centrally in the SC. The neuropeptide then activates the local cells to secrete neurotrophin‐3 (NT‐3), which mediates the survival and differentiation of donor stem cells overexpressing the NT‐3 receptor, at the injury/graft site of the SC. Increased local production of NT‐3 facilitates reconstruction of host neural tissue such as nerve fiber regeneration and myelination. All this events in sequence would ultimately strengthen the cortical motor‐evoked potentials and restore the motor function of paralyzed limbs. The information presented herein provides a basis for future studies on the clinical application of GV‐EA and adult stem cell transplantation for the treatment of SCI.

Intranasal calcitonin gene-related peptide administration impairs fear memory retention in mice through the PKD/p-HDAC5/Npas4 pathway

The calcitonin gene-related peptide (CGRP) suppresses fear memory retention in mice. Although intracerebroventricular administration of CGRP alters the fear memory processes, making it a promising therapeutic strategy for post-traumatic stress disorder (PTSD), direct brain injection into patients is not practical. Therefore, we propose that intranasal application may be an effective way to deliver CGRP to the brain. This study tested whether CGRP nasal administration exerts the same effect as intracerebroventricular administration using C57BL6J mice. The amount of CGRP in the cerebrospinal fluid and hippocampus 30 min after nasal administration of CGRP was significantly higher when compared with saline. Intranasal CGRP also elicited photophobic behaviors similar to intracerebroventricular injection. Moreover, intranasal CGRP decreased fear memory retention but did not affect reactivation and extinction of fear memory. We found intranasal CGRP significantly increased the expression of protein kinase D (PKD), phosphorylated histone deacetylase 5 (p-HDAC5) and neuronal PAS domain protein 4 (Npas4) in the hippocampus. CGRP-mediated impairment of fear memory and Npas4 expression increases were attenuated significantly by the CGRP receptor antagonist BIBN4096. Together, our data demonstrate that intranasal CGRP delivery activates the PKD/p-HDAC5/Npas4 pathway, decreases fear memory retention.

Involvement of TRPV1 in the expression and release of calcitonin gene-related peptide induced by rutaecarpine.

The traditional Chinese herb Wu-Chu-Yu has been used to treat hypertension for hundreds of years. A previous study indicated that rutaecarpine was the effective component of Wu-Chu-Yu, which lowered blood pressure by elevating the expression level of calcitonin gene-related peptide (CGRP). The present study was performed to investigate the role of transient receptor potential cation channel subfamily V member 1 (TRPV1) in CGRP expression and release induced by rutaecarpine. Dorsal root ganglia (DRG) obtained from Sprague-Dawley rats were cultured to analyze the mRNA expression and release of CGRP. Calcium influx, as an indicator of TRPV1 activation, was measured in 293 cells with stable overexpression of TRPV1. The results demonstrated that the amount of CGRP in the cell culture supernatant and the mRNA expression of CGRPα and CGRPβ in DRG was upregulated by rutaecarpine in a concentration-dependent manner, and was inhibited by the TRPV1 receptor antagonist capsazepine. In addition, intracellular Ca2+ levels were increased by Rut in the aforementioned 293 cell line, indicating the activation of TRPV1 by Rut. Therefore, it was concluded that TRPV1 was involved in the expression and release of CGRP stimulated by rutaecarpine, which provided novel mechanistic understanding of the treatment of hypertension using the Chinese herb Wu-Chu-Yu.

Effect of intracanal diode laser application and low-level laser therapy on CGRP change.

The aim of this study was to investigate the effect of a placebo, intracanal diode laser application, and low-level laser therapy (LLLT) on the change of the total amount of calcitonin gene-related peptide (CGRP) in the gingival crevicular fluid (GCF) (split-mouth study design). GCF sampling was performed on a contralateral tooth and experimental tooth (root canal-treated tooth) of thirty-nine patients. The patients were divided into three groups (n = 13), as follows: placebo (mock laser application), intracanal laser application, and LLLT. GCF sampling was repeated at the same sites (experimental and control teeth) one week after root canal treatment. The data were analyzed using the Pearson's correlation analysis and the independent-samples t-tests (p=0.05). In the placebo group, the total CGRP level changes in the GCF before and after treatment was significantly higher for experimental teeth than for control teeth (p<0.05). However, there was no significant difference between experimental and control teeth in the intracanal laser application and LLLT groups (p > 0.05). Intracanal laser application and low-level laser therapy have immunomodulation effects linked to the modulation of the total amount of CGRP in the GCF.

Effects of subcutaneous carbon dioxide on calcitonin gene related peptide and substance P secretion in rat skin.

To investigate the subcutaneous injection of carbon dioxide (CO2) on neuropeptides Calcitonin Gene-Related Peptide (CGRP) and Substance P (SP) secretion in rat skin. Fifty-six Wistar-EPM rats were distributed in two groups: one for CGRP analysis, the other for SP analysis. Each group was subdivided into four subgroups: control (Cont), control with needle (ContNd), CO2 injection (CO2Inj) and atmospheric air injection (AirInj) - with seven animals each. Sample analyses of partial skin were conducted by Western Blotting (WB). In SP group, there was a decrease in the amount of neuropeptides in subgroups CO2Inj and AirInj. Similarly, in CGRP group, there was a decrease in the amount of pro-CGRP neuropeptides (15 kDa) in subgroups CO2Inj and AirInj; Nevertheless, there was no decrease in the amount of CGRP (5 kDa) in any subgroups. Subcutaneous injection of CO2 and atmospheric air decreased the amount of Substance P and pro-Calcitonin Gene-Related Peptide (15 kDa) neuropeptides in rat skin.

Tapentadol inhibits calcitonin gene-related peptide release from rat brainstem in vitro

We have previously developed an in vitro model of rat brainstem explants. The latter release sizable amounts of calcitonin gene-related peptide (CGRP); basal release can be stimulated by such secretagogues as high KCl concentrations, veratridine or capsaicine. In this paradigm we investigated the activity of the analgesic agent tapentadol; the effects of tapentadol were compared to those of a classical opioid receptor agonist, morphine, and the selective noradrenaline reuptake inhibitor reboxetine. Morphine inhibited basal CGRP release, with statistical significance from 1nM onward and maximal (−44%) inhibition at 100μM. Morphine also inhibited K+-stimulated peptide release, with a significant effect from 1μM and maximal (−39%) decrease at 100μM, but failed to inhibit release stimulated by 10μM capsaicin. At variance, reboxetine had no effect on baseline CGRP outflow, but was able to inhibit both K+-stimulated [significant inhibition from 1μM onward and maximal (−37%) decrease at 100μM], and capsaicin-stimulated release [significant effect from 1μM and maximal (−31%) decrease at 100μM]. Likewise, tapentadol had no effect on baseline CGRP release up to 100μM, but decreased secretion stimulated by 56mM KCl or capsaicin, with significant effects from 0.1 and 1μM respectively; maximal inhibition over 56mM KCl and capsaicin stimuli was −29% and −31%, respectively. Naloxone antagonized the effect of morphine, but not those of reboxetine and tapentadol, on K+-stimulated CGRP secretion. In conclusion the present study provides consistent pharmacological evidence that tapentadol acts as a noradrenaline reuptake inhibitor agent in this experimental model.

An Exploratory Study of Salivary Calcitonin Gene‐Related Peptide Levels Relative to Acute Interventions and Preventative Treatment With OnabotulinumtoxinA in Chronic Migraine

To determine if baseline/interictal saliva calcitonin gene-related peptide (CGRP) levels would be lower in subjects with chronic migraine receiving onabotulinumtoxinA compared with those receiving saline. CGRP is considered central to the pathogenesis of episodic migraine, but its relationship to chronic migraine is less understood. OnabotulinumtoxinA is an effective treatment for chronic migraine and has been demonstrated to inhibit the vesicular release of CGRP. This was an exploratory, randomized, placebo-controlled, crossover pilot study of 20 subjects that received onabotulinumtoxinA and saline injection (placebo). The amount of CGRP in saliva samples collected on a nonheadache or low headache day, and prior to and after treatment of a headache exacerbation was measured. Daily headache records, medications, and response to treatment were recorded in a diary. A decrease in baseline/interictal saliva CGRP levels for subjects receiving onabotulinumtoxinA from 39.4 ± 7.5 pg CGRP/mg total protein after the first month to 25.5 ± 4.1 pg after the third month was observed. However, this difference did not reach significance nor was it significant when compared to the saline treatment. There was a reduction in the number of headache days for both onabotulinumtoxinA and saline over baseline throughout the active phases of the study. However, there was no statistical difference in headache days between groups. Subjects with a greater than 50% response to onabotulinumtoxinA had better 2-hour pain relief with acute treatment than non-responders to onabotulinumtoxinA or saline. While CGRP levels were not elevated during a migraine attack in chronic migraine subjects as has been reported in episodic migraine, there was an overall decrease in the baseline/interictal levels in response to onabotulinumtoxinA.

Influence of varying estrogen levels on trigeminal CGRP release in healthy women

Migraine is 2-3 times more prevalent in women than in men, with frequent perimenstrual attacks. TRPV1 receptors on sensory nerve endings of the trigeminal track are important in mediating migraine attacks by releasing the vasodilator calcitonin gene-related peptide (CGRP). Variation in estrogen levels during the menstrual cycle may have an influence on the sensitivity of the TRPV1 receptor or on the amount of CGRP in perivascular nerve terminals and hence on CGRP release. Capsaicin, the active ingredient of hot chili peppers, stimulates the TRPV1 receptor and causes CGRP-dependent vasodilatation [1]. We set up a model to study trigeminal CGRP release in humans. We compared the vasodilator effects of capsaicin application and electrical stimulation on the forehead skin. Healthy women, not using hormonal contraceptives (age: 18-45, n=14), were studied with a Laser Doppler Imager on day 19-21 of their menstrual cycle and on day 1-2 of their menstruation. A 0.2 mM and a 20 mM capsaicin solution were applied to the skin. In addition, iontophoresis of saline was performed as a TRPV1-independent stimulus. Increases in dermal blood-flow (DBF) were measured. Blood samples were collected to measure estrogen levels. We measured higher DBF responses to application of 0.2 mM capsaicin (Max:226±34 a.u.) and 20 mM capsaicin (Max:507±39 a.u.) during day 1-2 (low estrogen levels: 15±2 pg/ml) of the menstruation, than during day 19-21 (high estrogen levels: 67±9 pg/ml) of the menstrual cycle (Max:176±34 a.u. and 432±33 a.u. for 0.2 mM and 20 mM, respectively, P<0.05). There was no difference in DBF responses to electrical stimulation of the forehead skin, suggesting that the observed changes are related to the sensitivity of the TRPV1 receptor. Our results indicate an influence of variation in estrogen levels on trigeminal CGRP release, with the highest reactivity observed around the menstruation when estrogen levels are low. This mechanism may, at least partly, explain the high incidence of migraine attacks during the perimenstrual period.

Concentration of vasoactive intestinal polypeptide, neuropeptide Y and calcitonin gene related peptide in neoplastic tissue of the human large intestine

Aim of the study: The purpose of this study was to investigate the presence of vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and calci tonin gene related peptide (CGRP) neu ropeptides in neoplastic tissue of the large intestine. The results obtained were compared to an unchanged part of the intestine originating from the same patient. Material and methods: The tissue sam ples were taken from the postoperative part of the intestine, resected during an operation due to treatment of colon cancer. Tissues were taken from 15 patients. Concentrations of neu ropeptides were determined by ELISA tests, and results were calculated per 1 g of fresh tissue. The data obtained were statistically analysed. Results: In tissues of the neoplastic tumour of the sigmoid colon and rec tum the concentration of VIP and NPY was determined (28.9 ng/g and 8.6 ng/g, respectively). The observed values were statistically significantly lower than those observed in corresponding tissues of unchanged intestinal seg ments (83.9 ng/g for VIP and 19.5 ng/g for NPY). Surprisingly, amounts of CGRP were very similar in both neoplastic and intact tissues (13.3 ng/g and 13.4 ng/g respectively). Conclusions: Immunoenzymatic inves tigations allow one to establish the con centration of neuropeptides associated with the enteric nervous system in can cer tissues of the large intestine. Vari ous concentrations of these neuropep tides were observed in particular patients of both compared groups. The performed statistical analysis did not reveal associations between degree of cancer infiltration within the colonic wall and the level of presence of inves tigated neuropeptides in either cancer or control tissues. The fact of presence of these neuropeptides in cancer tissues confirmed by this study should be underlined at the same time.

The Study of Electroacupuncture on Cerebral Blood Flow in Rats With and Without Cerebral Ischemia

Electroacupuncture (EA) is widely used to treat disorders of the nervous system, such as stroke. The aim of the present study was to investigate the effect of EA on cerebral blood flow (CBF) in cerebral ischemic rats. We developed an animal model of cerebral ischemia (CI) by occluding the blood flow of both common carotid arteries in Sprague-Dawley (SD) rats; 2 or 15 Hz EA was applied to both Zusanli acupoints. The levels of nitric oxide (NO) in the peripheral blood and amounts of calcitonin gene-related peptide (CGRP) in the cerebral cortex and thalamus were measured. In addition, L-N (G)-nitro arginine methyl ester (L-NAME) was used to measure the changes in CBF induced by EA in rats with and without CI. The results indicated that both 2 and 15 Hz EA increase the mean CBF in rats with and without CI. However, neither 2 nor 15 Hz EA induced changes in levels of NO in peripheral blood or changes in CGRP levels in cerebral cortex and thalamus. In addition, L-NAME did not change the increase in CBF. We concluded that both 2 and 15 Hz EA at both Zusanli acupoints induced the increase of CBF in rats with and without CI. Whether the effect of EA is related to NO or CGRP will be investigated in a future study.

Regulation of calcitonin gene-related peptide secretion from trigeminal nerve cells by botulinum toxin type A: implications for migraine therapy.

To determine the effect of botulinum toxin type A on calcitonin gene-related peptide secretion from cultured trigeminal ganglia neurons. The ability of botulinum toxins to cause muscle paralysis by blocking acetylcholine release at the neuromuscular junction is well known. Previous studies and clinical observations have failed to demonstrate sensory changes related to botulinum toxins or the disease of botulism. Recent studies, however, have suggested that botulinum toxin type A injected into pericranial muscles may have a prophylactic benefit in migraine. This observation has renewed the debate of a mechanism of sensory inhibition mediated by botulinum toxin type A. Primary cultures of rat trigeminal ganglia were utilized to determine whether botulinum toxin type A could directly decrease the release of calcitonin gene-related peptide, a neuropeptide involved in the underlying pathophysiology of migraine. Untreated cultures or cultures stimulated with a depolarizing stimulus (potassium chloride) or capsaicin, an agent known to activate sensory C fibers, were treated for 3, 6, or 24 hours with clinically effective doses of botulinum toxin type A or a control vehicle. The amount of calcitonin gene-related peptide secreted into the culture media following the various treatments was determined using a specific radioimmunoassay. A high percentage (greater than 90%) of the trigeminal ganglia neurons present in 1- to 3-day-old cultures was shown to express calcitonin gene-related peptide. Treatment with depolarizing stimuli (potassium chloride), a mixture of inflammatory agents, or capsaicin caused a marked increase (4- to 5-fold) in calcitonin gene-related peptide released from the trigeminal neurons. Interestingly, overnight treatment of trigeminal ganglia cultures with therapeutic concentrations of botulinum toxin type A (1.6 or 3.1 units) did not affect the amount of calcitonin gene-related peptide released from these neurons. The stimulated release of calcitonin gene-related peptide following chemical depolarization with potassium chloride or activation with capsaicin, however, was greatly repressed by the botulinum toxin, but not by the control vehicle. A similar inhibitory effect of overnight treatment with botulinum toxin type A was observed with 1.6 and 3.1 units. These concentrations of botulinum toxin type A are well within or below the range of tissue concentration easily achieved with a local injection. Incubation of the cultures with toxin for 24, 6, or even 3 hours was very effective at repressing stimulated calcitonin gene-related peptide secretion when compared to control values. These data provide the first evidence that botulinum toxin type A can directly decrease the amount of calcitonin gene-related peptide released from trigeminal neurons. The results suggest that the effectiveness of botulinum toxin type A in the treatment of migraine may be due, in part, to its ability to repress calcitonin gene-related peptide release from activated sensory neurons.

Production and secretion of two vasoactive peptides, adrenomedullin and endothelin-1, by cultured human adrenocortical carcinoma cells

The production and secretion of peptides by adrenocortical tumors have not been well studied. We therefore studied the production and secretion of two vasoactive peptides, adrenomedullin and endothelin-1 in SW-13 human adrenocortical carcinoma cells by radioimmunoassay and Northern blot analysis. Both immunoreactive-adrenomedullin and immunoreactive-endothelin were detected in the culture medium of SW-13 cells (27.7 ± 1.6 fmol/10 5 cells/24 h and 11.0 ± 0.8 fmol/10 5 cells/24 h, respectively, mean ± SEM, n = 6). Northern blot analysis showed the expression of adrenomedullin mRNA and endothelin-1 mRNA in SW-13 cells. On the other hand, no significant amount of calcitonin gene-related peptide, corticotropin-releasing hormone, neuropeptide Y, or urocortin was secreted by SW-13 cells. Treatment with ACTH (10 −9–10 −7 mol/l), angiotensin II (10 −9–10 −7 mol/l), or dexamethasone (10 −8–10 −6 mol/l) for 24 h had no significant effects on immunoreactive-adrenomedullin levels and immunoreactive-endothelin levels in the culture medium of SW-13. Treatment with tumor necrosis factor (TNF)-α (20 ng/ml) increased significantly both immunoreactive-adrenomedullin levels and immunoreactive-endothelin levels in the culture medium. Interferon-γ (100 U/ml) increased the immunoreactive-endothelin levels, but not immunoreactive-adrenomedullin levels, whereas interleukin-1 (IL-1)β (10 ng/ml) increased immunoreactive-adrenomedullin levels, but not immunoreactive-endothelin levels. These findings indicate that SW-13 human adrenocortical carcinoma cells produce and secrete two vasoactive peptides, adrenomedullin, and endothelin-1 and that the secretion of these two peptides is modulated differently by cytokines.

Calcitonin gene-related peptide and prostaglandin E 2 but not substance P release induced by antidromic nerve stimulation from rat skin in vitro

The liberation of calcitonin gene-related peptide from rat skin in vitro induced by antidromic electrical stimulation of unmyelinated units is demonstrated. Prostaglandin E 2 was released concomitantly during C-fiber stimulation. A dose-dependent increase in prostaglandin E 2 content of the eluate was also observed in response to stimulation with substance P (10 −7 to 10 −5 M) and calcitonin gene-related peptide (10 −6 and 10 −5 M). In contrast, prostaglandin E 2 did not induce measurable release of neuropeptides. The amount of calcitonin gene-related peptide released during suprathreshold electrical stimulation increased with pulse frequency. Calcitonin gene-related peptide and prostaglandin release were completely inhibited in the presence of EMD 61753, a selective x-opioid receptor agonist. No significant release of substance P was observed. The data demonstrate a primary release of calcitonin gene-related peptide from unmyelinated but not myelinated primary afferents in the rat skin, which is accompanied by a secondary liberation of prostaglandin E 2, connecting neurogenic inflammation to general mechanisms of inflammation.

Decrease in CGRP and CT levels either contained in or released by CA-77 C cells after combined treatments with 1,25-dihydroxyvitamin D3 analogues and 9-cis retinoic acid.

This study examined the action of 9-cis retinoic acid and 1,25-dihydroxyvitamin D3 analogues (KH 1060, EB 1089 and MC 903) on the release of calcitonin (CT) and calcitonin gene-related peptide (CGRP) in the rat C cell line CA-77. This cell line mainly secretes CGRP. Using radioimmunoassays (RIAs) for CT and CGRP, we measured the release of both peptides in the culture medium as well as the amount of these proteins contained in the CA-77 C cells. 9-cis retinoic acid decreased the release of both CGRP and CT dose-dependently in the range between 1 nM and 1 microM. The half-effective dose was 10 nM. The treatment of CA-77 C cells with 0.1 microM calcitriol alone only slightly decreased the release of both CT and CGRP. The increase in the amount of CT and CGRP released by the action of 1 microM dexamethasone was reduced by 1 microM 9-cis retinoic acid, and this effect was enhanced by the addition of 0.1 microM calcitriol or KH 1060, EB 1089 and MC 903. When the C cells were continuously stimulated by dexamethasone, after 6 days of exposure to the combined treatment with calcitriol analogues + 9-cis retinoic acid, there was a greater decrease in the amount of CGRP contained in the C cells than after treatment with 9-cis retinoic alone. Our data suggested that combined treatment with retinoic acid and calcitriol analogues exerted a stronger inhibition on the amounts of the two peptides either contained in the cells or released in the medium than each hormone alone.

Increased susceptibility of rat gastric mucosa to ulcerogenic stimulation with aging

We examined the influences of aging on gastric damage and gastric mucosal blood flow (GMBF) responses induced by acid back-diffusion, following the barrier disruption, and investigated the relation of capsaicin-sensitive sensory nerves to these changes. Male Fischer rats 3, 13, and 24 months old were used. Under urethane anesthesia, a rat stomach was mounted on a chamber, and gastric potential difference (PD), luminal H+ loss, and GMBF were measured before, during, and after exposure to 20 mM sodium taurocholate (TC) for 30 min, in the presence of 50 mM HCl. Mucosal exposure to TC caused surface cell damage, PD reduction, and acid back-diffusion (luminal H+ loss) in all groups of rats; delta PD reduction and the amount of H+ loss were not significantly different between young and aged rats. In young rats, a marked increase of GMBF was observed with luminal acid loss following TC treatment, yet it resulted in less damage in the gastric mucosa. In aged rats, however, such GMBF responses were apparently mitigated, leading to a significant worsening of gastric mucosal lesions induced by TC. Mucosal application of capsaicin (0.1 mg/ml) caused an increase of GMBF in young rats, but this response was significantly attenuated in aged rats. In addition, the amount of calcitonin gene-related peptide (CGRP) released in the isolated stomach in response to capsaicin (1 X 10(-5) M) was significantly lower in aged animals when compared to young rats. These findings suggest that the gastric mucosa of aged rats is more vulnerable to acid back-diffusion following the barrier disruption, partly because of dysfunction of GMBF responses mediated by capsaicin-sensitive sensory neurons in the acidic conditions.

Changes in pulmonary calcitonin gene-related peptide and protein gene product 9.5 innervation in rats infected with Mycoplasma pulmonis.

Changes in the expression of calcitonin gene-related peptide (CGRP) and polyneural protein gene product 9.5 (PGP) in hilar peribronchial innervation was investigated by immunohistochemistry in specific pathogen-free rats chronically infected with Mycoplasma pulmonis. Image analysis of immunostained sections revealed a reduction of approximately 62% in the amount of CGRP- and PGP-immunoreactive innervation of the peribronchial area in the infected animals. The portion of the total bronchial perimeter occupied by bronchus-associated lymphoid tissue was increased six-fold. The decrease in the CGRP-immunoreactive area could be the result either of an enhanced CGRP release or of a loss of nerve fibres. The decrease in the PGP-immunoreactive fibres indicates a degenerative loss of nerves. Increased bronchus-associated lymphoid tissue and decreased bronchial innervation by neurons releasing the immunomodulatory neuropeptide CGRP might both contribute to the pathophysiology and symptoms of mycoplasmosis in the rat.

The effect of body weight on the calcitonin gene-related peptide-induced relaxation of guinea pig gallbladder strips

Calcitonin gene-related peptide (CGRP) has been reported to relax, in a concentration-dependent manner, cholecystokinin-induced tension in guinea pig gallbladder strips. It is now shown that this CGRP-induced relaxation is body weight dependent with the degree of relaxation inversely related to weight. Radioimmunoassay demonstrated that the amount of CGRP in the gallbladder increased with body weight. Receptor binding showed that the number of binding sites and the affinity of the receptor decreased with increasing body weight. CGRP may play a role in the normal pattern of gallbladder contraction and relaxation. Decreased motility, even between periods of complete emptying, has been demonstrated to have a role in gallbladder diseases. The decreased sensitivity of the gallbladder to CGRP may explain the increase in abnormalities with age.

Release of calcitonin gene‐related peptide from nerve terminals in rat skeletal muscle.

1. The amount of calcitonin gene-related peptide (CGRP) released from the isolated rat soleus muscle was measured by enzyme immunoassay. 2. When the soleus muscle was exposed to a solution containing high K+ (20-100 mM) in the presence of tetrodotoxin, the amount of CGRP released into the bathing medium increased with an increase in the K+ concentration. 3. The exposure to 100 mM-K+ did not increase CGRP release from chronically denervated soleus muscles or from pieces of the soleus nerve separated from the muscle. 4. The amount of CGRP released from the isolated muscle by 100 mM-K+ depended on the external Ca2+ concentration. The slope of the relation between the amount of CGRP release and the Ca2+ concentration was less than one on double logarithmic co-ordinates. 5. Following chronic section of the lumbar ventral roots, the mean amount of CGRP released from the soleus muscle by 100 mM-K+ was reduced by 28%, compared with that observed in normal muscle. 6. Antidromic stimulation of the lumbar dorsal roots at an intensity three times the threshold for most excitable sensory fibres failed to induce CGRP release from the soleus muscle, whereas stimulation at intensities 50-100 times the threshold increased significantly the amount of CGRP release from the muscle. 7. Stimulation of the muscle nerve at an intensity sufficient to activate the alpha-motor fibres did not release CGRP from the soleus muscle or from the diaphragm. 8. It is concluded that the major source of CGRP released from skeletal muscle is A delta- and/or C sensory terminals and that the Ca2+ dependence of CGRP release is less steep than that reported for acetylcholine release at neuromuscular junctions.

Influence of heat stimulation on the amount of calcitonin gene-related peptide and neurokinin A in the subcutaneous space of the rat hind instep.

The release of tachykinins and calcitonin gene-related peptide (CGRP) into subcutaneous perfusates was investigated. Immersion of the hind paw of rats in water at 47 degrees C for 30 min led to a marked increase of immunoreactive CGRP (iCGRP) release as well as immunoreactive substance P release, but no detectable increase of immunoreactive neurokinin A release. Neonatal pretreatment with capsaicin or section of the sciatic and the saphenous nerves significantly inhibited the heat stimulation-induced release of iCGRP.