Calcitonin gene-related peptide (CGRP) expression in the human neonatal paravertebral ganglia.

The distribution of calcitonin gene-related peptide-immunoreactivity (CGRP-IR) in human neonatal paravertebral ganglia was demonstrated by the method of indirect immunohistochemistry. A marked population (up to 21%) of CGRP-IR neurons and varicose nerve fibres was observed. The number of calcionin gene-related peptide-immunoreactive neurons varied from ganglion to ganglion in the sympathetic trunk. In addition to its cotransmitter functions, the existence of CGRP in neonatal ganglionic nerve cells was suggested by its inductive and trophic actions on the growth and differentiation of neurons.     

Calcitonin gene-related peptide (CGRP)-immunoreactive neurons in the human cervico-thoracic paravertebral ganglia

The occurrence of CGRP-immunoreactive neurons in human paravertebral sympathetic ganglia was investigated and CGRP-immunoreactive perikarya correlated with the distribution of structures which were immunoreactive to other peptides and tyrosine hydroxylase, the key enzyme of catecholamine-synthesis. CGRP-immunoreactive neurons were present in all investigated ganglia (superior cervical ganglion, stellate ganglion, thoracic ganglia IV and VII). Most of the CGRP-immunolabelled cell bodies contained also vasoactive intestinal polypeptide-as well as somatostatin-immunoreactivity. Approximately 40 per cent of the CGRP-immunoreactive neurons were weakly tyrosine hydroxylase-immunolabelled. CGRP-immunoreactive cell bodies appear to be neither identical with the large population of neuropeptide Y-labelled perikarya nor with the large group of cell bodies which were surrounded by leuenkephalin-immunoreactive nerve fibres. Colocalization of CGRP- with vasoactive intestinal polypeptide- and somatostatin-immunoreactivity in postganglionic sympathetic neurons substantiates the suggestion of sympathetic origin of respective peptidergic nerve fibres in sweat glands.     

Calcitonin gene-related peptide (CGRP) receptors are linked to cyclic adenosine monophosphate production in SK-N-MC human neuroblastoma cells

Calcitonin gene-related peptide (CGRP) stimulated cyclic adenosine monophosphate (cAMP) levels in SK-N-MC human neuroblastoma cells in a time- and concentration-dependent manner. The efficacy order for CGRPs was human alpha-CGRP = human beta-CGRP = chick CGRP greater than rat CGRP greater than human [Tyr0]CGRP. Calcitonin (CT) failed to influence cAMP production in SK-N-MC cells. [Tyr0]CGRP27-37 which by itself did not affect cAMP levels antagonized CGRP action. Saturation analysis using [125I]CGRP showed a homogeneous population of binding sites. CGRP but not CT, vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) inhibited radioligand binding. Our results provide evidence that human neuroblastoma SK-N-MC cells contain highly specific CGRP receptors which are positively coupled to cAMP generation.     

Calcitonin gene-related peptide (CGRP)-immunoreactive nerve terminals in the whole mount preparations of the dog urethra.

To visualize the entire shape of the intraepithelial nerve fibers, whole mount preparations of the dog urethra were produced and immunostained with an antiserum against CGRP, one of the predominant substances contained in the nerves. The immunoreactive nerves in the lamina propria were smooth (non-beaded) in appearance and weak in immunoreaction. Within the epithelium, they displayed typical beaded profiles and were intense in immunoreaction. The intraepithelial fibers branched and wound into an extensive network with wide meshes ("reticular terminal"). The bead-like swellings included large ones resembling Herring bodies in hypophyseal neurosecretory fibers. Another type of nerve terminal, consisting of fine and weakly immunopositive fibers, was also found in the epithelium. These branched in dendritic or in dense bouquet-like fashion, occupying smaller areas ("bouquet-like terminals). Vesicular swellings often characterized these terminals, though they were smaller and more uniform in size and far less in their amount of immunoreactive substance than were the swellings in the reticular terminals. Both types of nerve terminals originated from the same nerve trunk. The connection between the reticular and bouquet-like terminals, which may presumably represent secretory and receptive parts, respectively, morphologically supports the possible occurrence of an axon reflex in the urethral CGRP neurons. Our whole mount preparations, when doubly stained with CGRP and serotonin antibodies, further revealed the CGRP-positive reticular terminals being closely associated with serotonin- or CGRP-immunoreactive paraneurons dispersed in the epithelium.     

Calcitonin gene-related peptide (CGRP): Responsible for the increased blood flow induced by the stimulation of sensory nerves

Calcitonin gene-related peptide (CGRP) is a potent vasodilator neuropeptide contained in sensory nerves. We have examined the relative contribution of CGRP and substance P-like peptides (with which CGRP is commonly colocalized) to the increase in blood flow induced by the stimulation of sensory nerves. The sensory nerve stimulant capsaicin increased blood flow in rabbit and rat skin and this effect was substantially inhibited by the CGRP antagonist CGRP_8–37. Further, electrical stimulation of the rat saphenous nerve led to an increase in blood flow which was significantly inhibited by CGRP_8–37. CGRP_8–37 also had a partial inhibitory effect on oedema formation, an effect which is suggested to be a consequence of the inhibition of blood flow.     

Calcitonin gene-related peptide (CGRP): Responsible for the increased blood flow induced by the stimulation of sensory nerves

Calcitonin gene-related peptide (CGRP) is a potent vasodilator neuropeptide contained in sensory nerves. We have examined the relative contribution of CGRP and substance P-like peptides (with which CGRP is commonly colocalized) to the increase in blood flow induced by the stimulation of sensory nerves. The sensory nerve stimulant capsaicin increased blood flow in rabbit and rat skin and this effect was substantially inhibited by the CGRP antagonist CGRP_8–37. Further, electrical stimulation of the rat saphenous nerve led to an increase in blood flow which was significantly inhibited by CGRP_8–37. CGRP_8–37 also had a partial inhibitory effect on oedema formation, an effect which is suggested to be a consequence of the inhibition of blood flow.

     

Calcitonin gene-related peptide (CGRP) and leg vascular resistance during head-up tilt induced hypovolaemic shock in man

Calcitonin gene-related peptide is a potent vasodilator and its distribution in perivascular nerves suggests a role in the regulation of vascular tone. We evaluated leg vascular resistance together with total peripheral resistance and the arterial plasma concentrations of calcitonin gene-related peptide and catecholamines during 50 degrees head-up tilt induced hypotension in 7 males. During tilt mean arterial pressure, heart rate, total peripheral resistance, leg vascular resistance and plasma noradrenaline increased, while cardiac output and leg blood flow decreased. After 45 +/- 9 min (mean +/- SE) presyncopal symptoms appeared together with decreases in mean arterial pressure (81 +/- 6 to 56 +/- 9 mmHg), heart rate (97 +/- 6 to 73 +/- 8 beats min-1), leg vascular resistance (158 +/- 9 to 109 +/- 8 mmHg min l-1) and total peripheral resistance (17 +/- 3 to 10 +/- 2 mmHg min l-1) (P less than 0.01). Plasma calcitonin gene-related peptide increased from 32 +/- 3 to 35 +/- 3 pmol l-1 (P less than 0.01) and adrenaline from 1.1 +/- 0.2 to 1.7 +/- 0.3 nmol l-1 (P less than 0.01), while noradrenaline did not change. The results indicate that presyncopal symptoms induced by head-up tilt are associated with regional as well as total decreases in vascular resistance accompanied by moderate increases in arterial plasma concentrations of calcitonin gene-related peptide and adrenaline.     

The effect of calcitonin gene-related peptide (CGRP) on human forearm blood flow

The effect of intravenous and intra-arterially administered calcitonin gene-related peptide (CGRP) on the human forearm blood flow and cutaneous blood flow were investigated by means of venous occlusion plethysmography and laser-Doppler flowmetry, respectively. Infusion of CGRP (11-216 pmol min-1) into the brachial artery resulted in a dose-dependent increase in forearm blood flow and cutaneous blood flow which persisted for up to 90 min after the infusion was stopped. Repeated infusions resulted in an identical response. Systemic intravenous infusion of CGRP (104-520 pmol min-1) resulted in a dose-dependent flush in the face, neck, upper trunck and upper arms, and an increase in the forearm blood flow. The cutaneous blood flow was dramatically increased on the forehead, whereas on the hand only a slight increase was noted. By intravenous infusions a significant drop in blood pressure and increase in heart rate were seen at 520 pmol min-1. Thus, it is possible to give CGRP in doses that increase the blood flow in muscle and skin without resulting in a fall in systemic arterial blood pressure and tachycardia, suggesting that CGRP may be used as a tool for the treatment of various conditions in man with compromised blood flow.     

The calcitonin gene-related peptide (CGRP) antagonist CGRP(8-37) blocks vasodilatation in inflamed rat skin: involvement of adrenomedullin in addition to CGRP

The neuropeptide calcitonin gene-related peptide (CGRP) is a potent microvascular vasodilator in rat skin and effects are antagonised by CGRP_8–37. In this study, CGRP_8–37 significantly (P<0.05) inhibited the time-dependent (3–5 h) increase in skin blood flow measured in the anaesthetised rat, after intradermal administration of the inflammatory cytokine interleukin-1β (3 pmol/site), indicating the involvement of CGRP1 receptors. The CGRP-related peptide adrenomedullin (ADM) is also a potent vasodilator in rat skin, with effects antagonised by CGRP_8–37. We show that ADM mRNA expression is increased in rat skin after treatment with IL-1β and that the IL-1β-induced blood flow is blocked by a selective ADM antibody (P<0.05). Thus ADM is expressed locally in the inflamed cutaneous microvasculature where it can, in addition to, or as an alternative to CGRP, contribute to IL-1β-induced vasoactive effects.     

Calcitonin gene-related peptide (CGRP)-immunoreactive nerves in the tracheal epithelium of rats: an immunohistochemical study by means of whole mount preparations.

The airway mucosa is known to be densely supplied with several types of peptidergic nerve fibers. The distribution of the nerve fibers in a large extent of the mucosa, however, has been difficult to visualize by observation of conventional thin sections. In the present study, whole mount preparations of the rat tracheal mucosa were designed to demonstrate calcitonin gene-related peptide (CGRP)-containing nerves which are most predominant among peptidergic nerves in the trachea. The mucosal sheet of the trachea was separated from the cartilaginous base by means of dispase, a protease, to be processed to immunohistochemistry for CGRP. In the cartilaginous portion, thick nerve bundles immunoreactive for CGRP ran transversely between the cartilage rings, sending terminal branches toward the epithelium. In the membranous portion, immunoreactive nerve bundles were thinner than those in the cartilaginous portion and ran longitudinally. A very dense nerve plexus of CGRP-immunoreactive fibers was demonstrated to extend in the basal part of the epithelium; every epithelial cell appeared to contact more than one nerve fiber. Immunohistochemistry of the whole mount preparations also clearly demonstrated the distribution and entire shape of broncho-pulmonary paraneurons scattered in the epithelium. Ultrastructurally, the CGRP-immunoreactive intraepithelial nerves were found to lack myelin and Schwann sheaths, and to run through the bases of the epithelial cells; they were most frequently surrounded by the cytoplasmic processes of the epithelial cells. The present study demonstrates that immunohistochemistry of whole mount preparations is a useful tool to morphologically analyze neuronal and paraneuronal distribution throughout the tracheal epithelium.     

降钙素基因相关肽拮抗内皮素生物效应的研究

本实验在大鼠及小鼠的整体、离体器官及细胞水平上系统观察了降钙素基因相关肽对内皮素的拮抗作用。结果表明，ＣＧＲＰ显著地拮抗ＥＴ的升压、增加血管张力、促进血管平滑肌细胞增殖、损伤心肌以及致小鼠猝死等作用，并明显降低大鼠血浆ＥＴ含量。结果提示ＣＧＲＰ可能是机体内源性ＥＴ拮抗剂，给予外源ＣＧＲＰ可能对与ＥＴ有关的心脑血管疾病有防治意义。     

Calcitonin gene-related peptide (CGRP)-immunoreactive nerve varicosities in synaptic contact with sensory neurons in the trigeminal ganglion of rats

Immuno-light and -electron microscopic analyses revealed for the first time and reliably a substantial, although small, number of synapses between calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers and sensory neuron somata in the rat trigeminal ganglion. The CGRP-immunoreactive pericellular fibers forming the synapses survived the isolation and subsequent short-term incubation in the anterior eye chamber, indicating the intraganglionic origin of the pericellular fibers.     

Calcitonin gene-related peptide (CGRP) and transcutaneous electrical nerve stimulation (TENS) increase cutaneous blood flow in a musculocutaneous flap in the rat

The effect of blood flow on transcutaneous electrical nerve stimulation (TENS) and injection of calcitonin gene-related peptide (CGRP) was studied in a musculocutaneous flap of the rat, using laser Doppler flowmetry. The circulatory border was estimated before and after treatment. It was shown that repeated treatments with TENS gradually increased the blood flow, moving the circulatory border distally more than 100% after three treatments. Injection of NaCl into the dorsal central vein of the flap resulted in no increase in blood flow, whereas CGRP 10(-10) M increased the blood flow, so that the circulatory border moved distally 70% and 60%, respectively.     

Calcitonin gene-related peptide stimulates human villous trophoblast cell differentiation in vitro

Calcitonin gene-related peptide (CGRP) is a multifunctional peptide present in both maternal and fetal circulations in pregnancy. Its receptors have been identified on human trophoblast cells, but the role of CGRP in trophoblast differentiation remains unknown. This study was designed to determine the effect of CGRP on the differentiation of villous trophoblasts isolated from normal human term placentae. The morphological and functional differentiation of the trophoblast cells were assessed by desmosomal protein immunofluorescent staining and the quantification of hCG, estrogen and progesterone secretion. Results showed that (i) exposure of villous trophoblast cells to CGRP led to a dose-dependent increase in intracellular cyclic adenosine monophosphate (cAMP) accumulation; (ii) immunofluorescent staining with antidesmosomal antibody was identified at the boundaries between aggregated cytotrophoblast cells, and these stainings disappeared when cells fused to form syncytiotrophoblast cells; (iii) the formation of multinucleated syncytiums in primary cultured cytotrophoblasts was stimulated by CGRP as evidenced by the changes in antidesmosomal staining; (iv) CGRP increases trophoblast hCG secretion in a time- and dose-dependent manner, and this secretion was blocked by CGRP antagonist, CGRP(8-37), and (v) both 17beta-estradiol (E(2)) and progesterone concentrations in the culture medium were increased by CGRP, and these increases were dose dependent. These observations suggest that CGRP may be involved in the morphological and functional differentiation of trophoblast cells, and these actions might be attributed to CGRP-induced intracellular cAMP accumulation.     

Calcitonin gene-related peptide, adrenomedullin and flushing

Administration of calcitonin gene-related peptide (CGRP) or adrenomedullin (AM) can cause facial flushing, suggesting that the peptides may be important in hot flushes experienced particularly by post-menopausal women. Five studies have measured plasma CGRP concentrations in post-menopausal women who suffer from flushes; all demonstrated elevations of between 170% and 320% over control. Three of the studies showed a temporal relationship between flushes and CGRP elevation. A further study has shown that CGRP is elevated in the urine of women who suffer from flushes. Only a single study has investigated flushes in pre-menopausal women; no elevation of CGRP was observed. Flushes are also experienced by men undergoing androgen deprivation therapy. Whilst one study failed to find any increase in CGRP in the urine of these individuals, a small study has identified an increase in plasma CGRP. No studies have investigated plasma AM or the related peptide, intermedin/AM2. Overall, there is good evidence to show that flushes in post-menopausal women are accompanied by an increase in CGRP. CGRP could act centrally on the thermoregulatory centre of the hypothalamus as well as peripherally to cause vasodilation and sweating. However, it remains to be demonstrated that the elevated CGRP causes flushes. Recently developed CGRP antagonists provide an opportunity to test this hypothesis. If they are successful, they may represent a useful alternative to oestrogen replacement therapy.     

The contribution of calcitonin gene-related peptide (CGRP) to neurogenic vasodilator responses

The neuropeptide calcitonin gene-related peptide (CGRP) is a potent vasodilator in the microcirculation of many tissues including the skin and joint. In order to elucidate the mechanism of endogenous CGRP release, we have used a multiple site¹³³Xe clearance technique to measure local blood flow changes in response to agents injected intradermally in the rabbit. Capsaicin (100 nmol/site) and human αCGRP (3 pmol/site) stimulated similar increases in blood flow and, in both cases, the effect was totally abolished by the CGRP antagonist, CGRP_8–37 (1 nmol/site). By contrast, the nitric oxide synthase inhibitorl-nitro arginine methyl ester (l-NAME, 30 nmol/site) had little effect on human αCGRP-induced vasodilation, but caused significant inhibition of the response to capsaicin (p<0.05). These results show that increased blood flow in rabbit skin caused by exogenous CGRP is independent of nitric oxide. In addition, however, they suggest that nitric oxide is required for either the release of endogenous CGRP from capsaicin-sensitive nerves or its subsequent activity.     

降钙素基因相关肽（CGRP）在败血症休克中的作用

为探讨调节肽CGRP在休克中的发病学意义,本工作在结扎大鼠盲肠加穿孔的败血症休克模型上,观察了CGRP的变化及外源性CGRP对败血症休克过程的影响。结果发现,败血症休克时,血浆中CGRP显著增加(14.3±4.0 vs 5.5±1.8 Pg/ml,P<0.01)。在休克早期、晚期运用CGRP治疗(5μg/kg CGRP ⅳ)都能明显改善动物的低血压状态(分别是14.8±0.8,15.5±0.9 vs休克组10.3±1.6kPa,P<0.05),减轻心肌组织病理损伤,减少血浆中酶(LDH,CD)的漏出。同时,也可抑制休克动物血浆中AGT-Ⅱ含量的增加,提高血浆6-kcto-PGF_1α/TXB_2的比值(早期:69.1±5.3,晚期:65.8±4.1 vs休克组51.0±4.7%,P<0.05)。结果提示,CGRP可能参与败血症休克的代偿调节,适当应用CGRP治疗败血症休克是有益的。