Transient receptor potential vanilloid 1 and transient receptor potential ankyrin 1 contribute to the progression of colonic inflammation in dextran sulfate sodium-induced colitis in mice: Links to calcitonin gene-related peptide and substance P

Transient receptor potential (TRP) vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1), which are non-selective cation channels, play important roles in the sensation of pain. This study investigated the roles of TRPV1 and TRPA1 in dextran sulfate sodium (DSS)-induced murine colitis. DSS (2%) administered for 7 days caused severe colitis that was significantly less severe in TRPV1-deficient (TRPV1KO) and TRPA1-deficient (TRPA1KO) mice than that in wild-type (WT) mice. Similar colitis attenuations were observed in TRPV1KO and TRPA1KO mice but not in WT mice that had been transplanted with bone marrow cells from WT, TRPA1KO, or TRPV1KO mice. DSS treatment upregulated calcitonin gene-relative peptide (CGRP)- and substance P (SP)-positive nerve fibers in the colonic mucosa of WT mice. TRPV1KO and TRPA1KO mice showed significant reductions in the DSS-induced upregulation of SP, but the DSS-induced upregulation of CGRP was not reduced. Sensory deafferentation evoked by pretreatment with high doses of capsaicin markedly exacerbated DSS-induced colitis with reductions in DSS-induced upregulation of SP- and CGRP-positive nerve fibers. These findings suggest that neuronal TRPV1 and TRPA1 contribute to the progression of colonic inflammation. While these responses may be mediated by the upregulation of SP-mediated deleterious mechanisms, CGRP may be associated with protective mechanisms.     

Participation of vanilloid/capsaicin receptors, calcitonin-gene-related peptide and substance P in gastric protection of omeprazole and omeprazole-like compounds

The effects of omeprazole and different omeprazole-like compounds, associated with anti-ischaemic, antioxidant and poly(adenosine-diphosphate-ribose) polymerase (PARP) inhibitory properties, on the gastric acid secretion (4 h pylorus-ligated) and indomethacin-induced gastric mucosal damage connected with the specific immunohistochemical distribution of TRPV1, CRGP and SP during the effects of these compounds, were studied. The observations were carried out in CFY-strain rats (180–210 g), according to the standard methods and the above-mentioned parameters were studied in these experimental circumstances without and with application of different compounds. We found that: (1) all of the compounds dose-dependently inhibited the gastric acid secretion and mucosal damage; (2) the expression of TRPV1 receptor, CGRP and SP decreased significantly in both pylorusligated and indomethacin-treated animals and (3) the expression of TRPV1 and CGRP was reduced. Meanwhile, no change was obtained in SP expression during the gastric mucosal protection produced by omeprazole and omeprazole-like compounds. The conclusions were that (1) a functional overlap exists between the capsaicin-sensitive afferent and efferent vagal nerve during omeprazole effects; (2) chemical modification of omeprazole molecule offers a new pathway to obtain a new drug for the introduction in the clinical practice.     

Substance P and calcitonin gene-related peptide: immunohistochemical localisation and microvascular effects in rabbit skeletal muscle

Summary 1. The distribution and microvascular effects of substance P (SP) and calcitonin gene-related peptide (CGRP) were studied in the rabbit tenuissimus muscle using immunohistochemistry and intravital microscopy. 2. Individual fibers within nerve bundles and along blood vessels in the muscle were found to be immunoreactive (IR) for both SP and CGRP, thus showing an apparently complete coexistence for these peptides. In dorsal root ganglia most SP-positive cells were also CGRP-IR, but the latter cells were somewhat more numerous than SP-IR cells. 3. When applied topically to the muscle, both SP and CGRP increased blood flow in a dose-dependent manner, but CGRP was more potent and caused responses of longer duration. Both SP and CGRP dilated transverse arterioles, but they had little or no effect on the smaller terminal arterioles. This resulted in a redistribution of blood flow to the connective tissue adjacent to the muscle. 4. SP, but not CGRP, elicited vigorous vasomotion in larger arterioles and caused the formation of aggregates of platelets and leukocytes in the venules. Neither flow increase, nor vasomotion or aggregate formation were influenced by pretreatment of the animals with mepyramine, cimetidine or indomethacin. Capsaicin (1 M) had a powerful effect on transverse arterioles resembling that of both SP and CGRP. 5. It is concluded that some of the vascular effects hitherto ascribed to SP on the basis of nerve stimulation and application of capsaicin might, at least in part, be due to release of CGRP. Send offprint requests to: A. Ohlen, Department of Physiology, Karolinska Institutet, S-104 01 Stockholm, Sweden     

Age-related changes in substance P-immunoreactive nerve structures of the rat recto-anal region

The recto-anal region is innervated by extrinsic and intrinsic nerves and a number of neuropeptides including substance P (SP) have been suggested to participate in the regulation of intestinal movements. We examined the age-related changes in the distribution of SP-immunoreactive nerve structures in the distal part of the rat large intestine. Using immunohistochemistry, the presence of SP was studied in fresh tissues from Wistar rats at different ages taken at three sampling sites, the distal rectum, anal canal and internal anal sphincter. In the 15-day old rats the myenteric plexus of the distal rectum and anal canal was well outlined by numerous SP-immunoreactive varicose nerve fibres encircling immunonegative perikarya. In the circular muscle layer, nerve fibres and small nerve bundles ran parallel to the muscle cells, while in the longitudinal muscle layer, only occasional nerve fibres were seen. At the level of the internal anal sphincter, no myenteric ganglia were present. Here, thin varicose fibers ran parallel to the smooth muscle cells. In the 3-month old rats, a larger number of intensely staining SP-immunoreactive nerve fibres were found and in the circular muscle layer, thicker nerve strands were observed. In the 26-month old rats, the density and staining intensity of SP-immunopositive nerve fibres in the myenteric plexus was lower than in the 3-month-old rats. Similar changes in the SP-immunostained fibres in the internal anal sphincter were observed. Degenerative alterations in SP-containing fibres during aging appear to play a role in ano-rectal motility and sphincter control.     

Co-existence of substance P and calcitonin gene-related peptide-like immunoreactivities in sensory nerves in relation to cardiovascular and bronchoconstrictor effects of capsaicin

Immunohistochemical studies showed that substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactivity co-exist in capsaicin-sensitive primary sensory neurons. Varicose SP- and CGRP-immunoreactive nerve fibres with a similar distribution pattern were seen in the lower airways and heart. The functional analysis revealed that CGRP caused cardiac stimulation and had, together with SP and neurokinin A, potent hypotensive effects. Vascular permeability was increased by SP and neurokinin A, and the bronchial smooth muscle was particularly sensitive to neurokinin A. Thus, multiple peptides stored in an possible released from the same nerve endings by capsaicin may exert differential effects in various target tissues.     

Substance P immunoreactive neurons following neonatal administration of capsaicin

Summary Neonatal administration of capsaicin on the days 2, 10 or 20 leads to a long-lasting loss of substance P immunoreactive material in fibers of primary sensory neurons in the spinal cord and medulla oblongata. The degree of depletion examined 6 months after treatment was related to the day of injection. Injections on the second day produced dramatic losses of substance P in fibers of the substantia gelatinosa and the marginal layer of the spinal cord and the spinal nucleus of the trigeminal nerve, although these losses were never complete. The observed depletion of substance P immunoreactive material was homogenous throughout the superficial layers of the dorsal horn and the spinal nucleus of the trigeminal nerve. No changes were observed for the immunoreactivity of Leu-enkephalin in the substantia gelatinosa and the marginal layer of the spinal cord in consecutive sections from the same treated animals. In the medulla oblongata a reduction of substance P immunofluorescent fibers was found in the nucleus tractus solitarii and the spinal nucleus of the trigeminal nerve. Other areas of the central nervous system with a rich innervation of substance P immunoreactive fibers were not affected by capsaicin treatment.     

Immunohistochemical distribution of vanilloid receptor, calcitonin-gene related peptide and substance P in gastrointestinal mucosa of patients with different gastrointestinal disorders

The immunohistochemical distribution of capsaicin/vanilloid (transient receptor potential vanilloid 1, TRPV1) receptors and neuropeptides (CGRP, SP) was studied in the gastrointestinal mucosal biopsies of patients with gastritis, erosions, ulcers, polyps, adenocarcinoma, chronic inflammatory bowel diseases, polyps without and with hyperplasia, dysplasia and adenocarcinoma in colon. The studies were carried out in 127 patients and 30 people with only functional dyspepsia (without any histological alteration). The results were: (1) the positivity of TRPV1 receptor and CGRP was detected, and weak participation of SP was detected in patients with different gastric diseases; (2) the presence of TRPV1, CGRP and SP could be detected in chronic inflammation of bowel disease; (3) SP could not detected in patients with colon polyps, dysplasia and adenocarcinoma; (4) the presence of TRPV1 and CGRP was proved in colon dysplasia and adenocarcinoma. We conclude that (1) the immunohistochemical distribution of TRPV1, CGRP and SP differs in gastrointestinal diseases of the upper and lower tract, and (2) the participation of TRPV1, CGRP and SP differs significantly in these different gastrointestinal diseases.     

TRPV1和TRPV4通道参与缺血/氧处理心血管保护的研究进展

TRPV通道属于瞬时受体电位(transient receptor potential,TRP)通道,含有TRPV1、TRPV2、TRPV3、TR-PV4、TRPV5和TRPV6等多种亚型,它们参与机体痛觉、味觉、体温等多种生理机能的调控.近期研究发现TRPV1和TRPV4通道可能参与缺血/氧处理诱导的心肌与血管保护.TRPV1通道的作用机制可能与降钙素基因相关肽(CGRP)及P物质的释放、花生四烯酸脂氧合酶(ALOX)的表达增多有关;TRPV4通道介导的血管保护机制可能与NO和EDHF介导的内皮源性舒张有关.本文将对TRPV1和TRPV4通道在不同形式缺血/氧处理诱导下的心血管保护机制进行综述,以期为心肌缺血的治疗提供新方向.     

Effect of denervation on the neurogenic inflammation of the rat mandibular mucosa

Summary Effects of local exposure to capsaicin on the vascular permeability and blood flow were studied in the rat oral mucosa at days 2 and 14 after the unilateral transcection of the inferior alveolar nerve (IAN). The distribution of nerve fibers displaying substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactivity (IR) in the mandibular mucosa was also assessed.While the capsaicin-induced augmentation in vascular permeability was about 50% (P < 0.05) higher on the intact side (at both days 2 and 14) than on the denervated side, no difference in blood flow elevation was seen between the two sides. Transection of IAN caused only a slight reduction in the density of SP- and CGRP-IR fibers in the mucosa.It is concluded that in addition to the IAN fibers the mandibular mucosa examined also seems to be supplied by other sensory fibers. The presence of accessory trigeminal branches was also supported by immunohistochemical studies.     

克隆病P物质阳性神经组织及肥大细胞的形态学观察

目的：观察克隆病时Ｐ物质阳性神经组织、肥大细胞形态变化,并探讨其在该病发病中的作用。方法;应用免疫组织化学,组织化学方法对２７例克隆病（回肠１４例,结肠１３例）,１０例对照组肠壁Ｐ物质（ＳＰ）阳性神经纤维,神经元及肥大细胞进行观察。用形态计量学方法计量ＳＰ阳性神经组织的体密度及肥大细胞密度。结果：克隆病时肠壁粘膜下层神经纤维增生,部分呈“神经瘤样”改变,ＳＰ阳性神经元数量增多。粘膜下层及肌间神经丛     

Multiple impairments of cutaneous nociceptor function induced by cardiotoxic doses of Adriamycin in the rat

Besides their deleterious action on cardiac muscle, anthracycline-type cytostatic agents exert significant neurotoxic effects on primary sensory neurons. Since cardiac sensory nerves confer protective effects on heart muscle and share common traits with cutaneous chemosensitive nerves, this study examined the effects of cardiotoxic doses of adriamycin on the function and morphology of epidermal nerves. Sensory neurogenic vasodilatation, plasma extravasation, and the neural CGRP release evoked by TRPV1 and TRPA1 agonists in vitro were examined by using laser Doppler flowmetry, the Evans blue technique, and ELISA, respectively. Carrageenan-induced hyperalgesia was assessed with the Hargreaves method. Immunohistochemistry was utilized to study cutaneous innervation. Adriamycin treatment resulted in profound reductions in the cutaneous neurogenic sensory vasodilatation and plasma extravasation evoked by the TRPV1 and TRPA1 agonists capsaicin and mustard oil, respectively. The in vitro capsaicin-, but not high potassium-evoked neural release of the major sensory neuropeptide, CGRP, was markedly attenuated after adriamycin treatment. Carrageenan-induced inflammatory hyperalgesia was largely abolished following the administration of adriamycin. Immunohistochemistry revealed a substantial loss of epidermal TRPV1-expressing nociceptive nerves and a marked thinning of the epidermis. These findings indicate impairments in the functions of TRPV1 and TRPA1 receptors expressed on cutaneous chemosensitive nociceptive nerves and the loss of epidermal axons following the administration of cardiotoxic doses of adriamycin. Monitoring of the cutaneous nociceptor function in the course of adriamycin therapy may well be of predictive value for early detection of the deterioration of cardiac nerves which confer protection against the deleterious effects of the drug.     

The role of transient receptor potential ankyrin 1 (TRPA1) receptor activation in hydrogen-sulphide-induced CGRP-release and vasodilation

Activation of transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) channels on capsaicin-sensitive sensory neurons causes release of inflammatory neuropeptides, including calcitonin gene-related peptide (CGRP). We investigated whether the hydrogen sulphide (H(2)S)-evoked CGRP release from sensory neurons of isolated rat tracheae and H(2)S-induced increases in the microcirculation of the mouse ear were mediated by TRPA1 receptor activation. Allylisothiocyanate (AITC) or the H(2)S donor sodium hydrogen sulphide (NaHS) were used as stimuli and CGRP release of the rat tracheae was measured by radioimmunoassay. AITC or NaHS were applied to the ears of Balb/c, C57BL/6, TRPA1 and TRPV1 receptor gene knockout mice and blood flow was detected by laser Doppler imaging. Both AITC and NaHS increased CGRP release from isolated rat tracheae, and both responses were inhibited by the TRPA1 antagonist, HC-030031, but was not affected by the TRPV1 receptor blocker, BCTC. Application of AITC or NaHS increased the cutaneous blood flow in the mouse ears. Similarly to the effect of AITC, the vasodilatory response to NaHS was reduced by HC-030031 or in TRPA1 deleted mice. In contrast, genetic deletion of TRPV1 did not affect the increase in the ear blood flow evoked by AITC or NaHS. We conclude that H(2)S activates TRPA1 receptors causing CGRP release from sensory nerves of rat tracheae, as well as inducing cutaneous vasodilatation in the mouse ear. TRPV1 receptors were not involved in these processes. Our results highlight that TRPA1 receptor activation should be considered as a potential mechanism of vasoactive effects of H(2)S.     

Peptide neuroanatomy of adjuvant-induced arthritic inflammation in rat

The influence of adjuvant-induced arthritis of the rat on central and peripheral peptide neuroanatomy was investigated by immunohistochemistry. The most striking feature of arthritic rats was the differential intensification of neuronal proenkephalin- and prodynorphin-related staining in dorsal horn. Changes were ipsilateral in monoarthritic and bilateral in polyarthritic rats as compared to controls. Opioid responsive neurons were target of substance P (SP) and calcitonin gene-related peptide (CGRP) fibers. Changes of SP and CGRP predominated in peripheral inflamed tissue and consisted of intensified immunostaining and an apparent sprouting of sensory fibers particularly around venules, in the epidermis and in areas infiltrated by immunocompetent cells. Opioid staining was absent from primary afferents but present in some immune cells of inflamed tissue. Endogenous antinociceptive opioids and pro-nociceptive/pro-inflammatory SP and CGRP may be crucial in the concerted response of the neuroimmune system to chronic inflammatory pain.     

Primary sensory neurons expressing histamine H1-receptor mRNA

Pharmacological studies have suggested that a subgroup of primary sensory neurons is responsive to histamine via the H1 receptor. However, which type of primary sensory neurons express H1 receptor is not known. We addressed this issue using in situ hybridization histochemistry with a cRNA probe for the guinea pig H1 receptor mRNA. H1 receptor mRNA was expressed in about 15-20% of the trigeminal and lumbar dorsal root ganglion (DRG) neurons, but none of the nodose ganglion neurons. The positive neurons in DRG were exclusively small in size and were labeled by isolectin B4, suggesting that these neurons have unmyelinated fibers. However, H1-receptor mRNA-expressing DRG neurons were not immunoreactive to substance P (SP) or calcitonin gene-related peptide (CGRP), which are implicated in the nociceptive transmission of the primary sensory system. Moreover, in guinea pigs neonatally treated with capsaicin (50 mg/kg), few CGRP-immunoreactive neurons were seen in DRG, but the percentage of H1-receptor mRNA-expressing neurons (15%-20%) and the intensity of the mRNA signals in these neurons were not affected by neonatal capsaicin treatment, suggesting that H1 receptor-expressing neurons are not sensitive to capsaicin. These findings suggest that H1-receptor-expressing neurons are involved in the transmission of a unique sensory modality such as itch. A marked increase in the number of mRNA-positive DRG neurons was observed 1-5 days after a crush injury of the sciatic nerve (3-4-fold of the control value). These neurons that turned mRNA-positive after the nerve crush were also mainly small-sized. The mRNA signals were detected in many peptidergic (SP/CGRP) neurons, in contrast to the normal condition. On the other hand, mRNA signals were decreased in the neurons that showed intense labeling in the normal condition. These results suggest that the gene expression of H1 receptors up-regulated in injured afferents may be involved in neuropathic pain.     

GABAergic neurons in the mammalian intestine

Most of the criteria for identification of a neurotransmitter were satisfied for gamma-aminobutyric acid (GABA) in the mammalian intestine. GABA and its synthesizing enzyme, glutamic acid decarboxylase, and the neurons which specifically accumulate GABA were demonstrated to localize in Auerbach's plexus of the intestine. GABA was demonstrated to be released from nerve terminals of the intestine when the nerve fibers were stimulated. The application of GABA depolarized the neurons within Auerbach's plexus. The actions of GABA were mimicked by muscimol on the GABAA receptor and by baclofen on the GABAB receptor. The GABAA antagonist is bicuculline, but no antagonist to GABAB is known at present. Thus, GABAergic neurons may be present in the enteric nervous system of the intestine. GABA and bicuculline changed the propulsive activity and the spontaneous motility of circular muscle, and the neuronal interactions, substance Pergic-GABAergic-postganglionic cholinergic neurons were found in the enteric nervous system, thereby suggesting that GABAergic neurons play a key role in the control of peristalsis.     

P2Y受体介导大鼠胃体环行肌收缩反应的药理学特点

观察大鼠离体胃体环行肌和胃底环行肌不同的药理学特征，分析核苷及核苷酸类物质诱发胃体环行肌收缩反应的作用特点和受体机制。制备大鼠离体胃体环行肌和胃底环行肌标本，利用受体药理学技术观察药物诱发的收缩反应。在胃体环行肌KCl所致收缩反应与胃底环行肌无显著性差别；但是，CCh收缩胃体环行肌的EC₅₀值 [(0.45 ± 0.15) μmol·L⁻¹] 显著高于胃底环行肌 [(0.20 ± 0.09) μmol·L⁻¹, P < 0.01]。5-HT和His收缩两种标本的EC₅₀值无显著差异 (P > 0.05); 但是, 在胃体环行肌5-HT和His产生收缩反应的E_max值 [(0.81 ± 0.26) 和 (0.88 ± 0.27) g] 显著小于胃底环行肌 [(2.67 ± 0.61) 和 (1.90 ± 0.68) g, P < 0.01]。在预收缩胃体环行肌，ATP (0.1～3 000 μmol·L⁻¹) 诱发浓度依赖性收缩反应，未见舒张反应；在预收缩胃底环行肌标本，同浓度ATP诱发先舒张后收缩的双相反应，并呈浓度依赖性。ATP、UTP、ADP、2-MeSATP和α, β-MeATP浓度依赖性诱发大鼠胃体环行肌收缩反应，2-MeSATP的EC₅₀值为 (7.2 ± 5.2) nmol·L⁻¹比Ach [(3.47 ± 1.20) μmol·L⁻¹] 低500倍；各药物产生收缩反应的效价序列为：2-MeSATP>>ADP>ATP=UTP>α, β-MeATP>>腺苷。酚妥拉明、普萘洛尔、阿托品及河豚毒素不影响ATP和UTP诱发的胃体环行肌收缩反应。研究结果表明, 大鼠胃体环行肌的药理学特征明显不同于胃底环行肌; 核苷酸类物质通过某种特殊的P2Y受体介导胃体环行肌收缩反应，是调节胃体环行肌收缩功能的重要介质。
     

Electrophysiological effects of activating the peptidergic primary afferent innervation of rat mesenteric arteries

1. Intracellular recording was used to investigate the electrophysiological effects of activating peptidergic primary afferent axons with capsaicin in the smooth muscle of rat mesenteric arteries in vitro. In addition, continuous amperometry was used to monitor the effects of capsaicin on noradrenaline release from the sympathetic nerves. 2. Capsaicin (1 microm) produced a hyperpolarization (-11+/-2 mV) and a reduction in the time constant of decay of excitatory junction potentials (e.j.p.'s) evoked by electrical stimulation of the perivascular sympathetic nerves. These effects of capsaicin were mimicked by calcitonin gene-related peptide (CGRP; 1 and 10 nm) but not by substance P (50 nm), which produced a small hyperpolarization (maximum -3+/-1 mV) but did not change excitatory junction potential (e.j.p.) time course. 3. The hyperpolarization produced by capsaicin and CGRP was blocked by glibenclamide (10 microm) but was not changed by the CGRP antagonist, CGRP8-37 (0.5 microm). Mechanical denudation of the endothelium also did not reduce the effect of capsaicin on membrane potential. 4. Capsaicin (1 microm) increased the amplitude of e.j.p.'s. This effect was not mimicked by CGRP or substance P nor blocked by glibenclamide or CGRP8-37. 5. All effects of capsaicin desensitized. 6. Capsaicin (1 microm) had no effect on noradrenaline-induced oxidation currents evoked by electrical stimulation, indicating that noradrenaline release was unchanged. 7. These results suggest that CGRP released from primary afferent axons hyperpolarizes vascular smooth muscle by activating glibenclamide-sensitive K+ channels. The findings also indicate that an unknown factor released by the primary afferent axons increases e.j.p. amplitude.     

Investigation of the potential modulatory effect of biliverdin,carbon monoxide and bilirubin on nitrergic neurotransmission in the pig gastric fundus

In porcine gastric fundus, we have investigated the colocalization of the bile pigment biosynthetic enzymes heme oxygenase-2 and biliverdin reductase with neuronal nitric oxide synthase (nNOS), the effect of carbon monoxide (CO) on fundic circular smooth muscle and the possible modulatory effect of the bile pigments biliverdin and bilirubin on CO-mediated relaxations and on nitrergic relaxation. Heme oxygenase-2 and biliverdin reductase immunoreactivity was present in all nNOS containing myenteric neurons. CO induced a concentration-dependent relaxation of fundic circular smooth muscle strips, which was completely blocked by the specific guanylate cyclase inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ). 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1), biliverdin and bilirubin strongly enhanced the amplitude of the CO-induced relaxation. Tin protoporphyrin had no effect on electrically induced nitrergic relaxation, but spectrophotometric analysis learned that incubation of porcine gastric fundus circular muscle strips with tin protoporphyrin did not influence heme oxygenase activity. In conclusion, our data suggest that nitrergic neurons in the pig gastric fundus are able to produce biliverdin and bilirubin, and that these agents potentiate the relaxant effect of CO, which is formed concomitantly with biliverdin by heme oxygenase-2.     

Cetraxate raises levels of calcitonin gene-related peptide and substance P in human plasma

Cetraxate hydrochloride (cetraxate), an anti-ulcer drug, produces a dose-related increase in mucosal blood flow. Recently, it was found that capsaicin-sensitive afferent nerves play an important role in gastric mucosal defence. Capsaicin stimulates afferent nerves and enhances the release of calcitonin gene-related peptide (CGRP) and substance P in the stomach. We studied the effect of cetraxate on human plasma CGRP and substance P in healthy subjects. Cetraxate (800 mg) or placebo were orally administered to five healthy males. Blood samples were taken before, and at 20, 40, 60, 90, 120, 180 and 240 min after administration, followed by the extracting procedure, and submitted to a highly sensitive enzyme immunoassay system for CGRP and substance P. Single administration of cetraxate caused significant increases in plasma CGRP concentration at 60-120 min compared with placebo. Cetraxate significantly increased plasma substance P levels at 40-90 min compared with placebo. In this study, we hypothesized that cetraxate might indirectly stimulate capsaicin-sensitive afferent nerves and increase mucosal blood flow, and that this may be a key mechanism underlying its gastroprotective action.