Acute and chronic stress differently affect visceral sensitivity to rectal distension in female rats

Stressful life events are frequently associated with outward signs of irritable bowel syndrome (IBS). Increasing evidence suggests that acute and chronic stress stimuli implicate different physiological mechanisms and neuroendocrine responses. Therefore, we investigated the influence of acute and chronic stress on visceral nociception in female rats and the involvement of colonic mast cells in this effect. The effect of acute and chronic partial restraint stress (PRS) on visceral sensitivity to rectal distension (RD) was assessed by abdominal muscle electromyography. Colonic mast cell activation was determined by measuring histamine release after in vitro stimulation with substance P (SP) in colonic samples from rats experiencing RD vs. controls. Acute PRS significantly enhanced abdominal response to RD compared with sham PRS for all volumes of distension. In contrast, chronic PRS induced a hyperalgesic response for the highest volumes of distension (0.8 and 1.2 mL), but did not affect the number of abdominal contractions for the lowest volume (0.4 mL) compared with controls. Both acute and chronic PRS increased in vitro SP-induced histamine release without affecting mast cell numbers. RD induced similar in vitro histamine release from colonic samples from both acute and chronic PRS rats; this release, however, was significantly higher than that measured in sham-PRS rats. Acute and chronic PRS differently influence visceral sensitivity in response to RD in female rats. This difference, however, cannot be attributed to a different effect of either stress paradigm on mast cell histamine release.

Intracellular signal transduction during gastrin-induced histamine secretion in rat gastric ECL cells

Activation of G(q) protein-coupled receptors usually causes a biphasic increase in intracellular calcium concentration ([Ca(2+)](i)) that is crucial for secretion in nonexcitable cells. In gastric enterochromaffin-like (ECL) cells, stimulation with gastrin leads to a prompt biphasic calcium response followed by histamine secretion. This study investigates the underlying signaling events in this neuroendocrine cell type. In ECL cells, RT-PCR suggested the presence of inositol 1,4,5-trisphosphate receptor (IP(3)R) subtypes 1-3. The IP(3)R antagonist 2-aminoethoxydiphenyl borate abolished both gastrin-induced elevation of [Ca(2+)](i) and histamine release. Thapsigargin increased [Ca(2+)](i), however, without inducing histamine secretion. In thapsigargin-pretreated cells, gastrin increased [Ca(2+)](i) through calcium influx across the plasma membrane. Both nimodipine and SKF-96365 inhibited gastrin-induced histamine release. The protein kinase C (PKC) activator phorbol 12-myristate 13-acetate induced histamine secretion, an effect that was prevented by nimodipine. In summary, gastrin-stimulated histamine release depends on IP(3)R activation and plasmalemmal calcium entry. Gastrin-induced calcium influx was mediated by dihydropyridine-sensitive calcium channels that appear to be L-type channels activated through a pathway involving activation of PKC.

Effects of interleukin-8 and Helicobacter pylori on histamine release from isolated canine gastric mucosal mast cells

BACKGROUND

In recent studies, the involvement of mast cells in the pathogenesis of Helicobacter pylori infection was suggested. In the present study, using isolated canine gastric mucosal mast cells, we undertook to elucidate the effects of interleukin-8 (IL-8) and H. pylori on histamine release from these cells.

METHODS

Enriched canine gastric mucosal mast cells (50% target cells) were incubated in Hanks medium with IL-8, or water extract or sonicate of H. pylori for 15 min at 37 degrees C. The content of histamine in the supernatants and the cell pellets after centrifugation was assayed with a histamine radioimmunoassay (RIA) kit.

RESULTS

IL-8 (50 ng/ml) and concanavalin A (20 microg/ml) significantly increased histamine release from enriched gastric mucosal mast cells. Dose-dependent stimulation of histamine release by IL-8 (5-50 ng/ml) was also seen. Water extract and sonicate of H. pylori (10(8) bacteria) increased histamine release from mast cells. A concentration-dependent stimulation of histamine release by water extract or sonicate was also seen. The maximal response of histamine release was seen at the highest concentration of the water extract or sonicate.

CONCLUSIONS

The results indicated that IL-8 and H. pylori had stimulatory effects on histamine release from canine gastric mucosal mast cells. The results imply that IL-8 and soluble factors of H. pylori may accelerate inflammation of the gastric mucosa via histamine release from mast cells.

Mouse light/dark box test reveals anxiogenic-like effects by activation of histamine H1 receptors

Effects of substances that are able to alter the histamine level, a histamine H(1)-receptor agonist and antagonist, and a histamine H(2)-receptor agonist were investigated in an anxiety-like state in mice by means of the light/dark box test. Diazepam was used as positive control. The histamine H(3)-receptor antagonist, thioperamide (2, 5, and 20 mg/kg s.c.), showed an anxiogenic-like effect that reached a maximum with the dosage of 5 mg/kg. The histamine-N-methyltransferase (HMT) inhibitor, metoprine (5 and 20 mg/kg s.c.), also decreased the time in the light at the highest dose used and, likewise, the highly selective histamine H(1)-receptor agonist, 2-(3-trifluoromethylphenyl)histamine (FMPH) (2.65 and 6.5 microg/mouse, i.c.v.). On the contrary, the histamine H(2)-receptor agonist, impromidine (3, 10, 20, and 30 microg/mouse, i.c.v.), dose-dependently showed an anxiolytic-like effect. The selective histamine H(1) antagonist, pyrilamine (20 mg/kg i.p.) was able to prevent the anxiogenic-like effect of FMPH significantly, and that of thioperamide partially, while the effect caused by metoprine remained unvaried. It is suggested that the histaminergic system modulates anxiety-like states via the activation of both postsynaptic receptors in a contrasting manner: activation of the H(1) receptor causes an anxiogenic-like effect, while that of the H(2) receptors reduces anxiousness. However, on the basis of effects observed with the substances capable of releasing endogenous histamine, it seems likely that the anxiogenic-like effect is prevalent.

Further studies on the structural requirements for mast cell degranulating (MCD) peptide-mediated histamine release

Mast cell degranulating (MCD) peptide was modified in its two disulfide bridges and in the two arginine residues in order to measure the ability of these analogs to induce histamine release from mast cells in vitro. Analogs prepared were [Ala(3,15)]MCD, [Ala(5,19)]MCD, [Orn(16)]MCD, and [Orn(7,16)]MCD. Their histamine-releasing activity was determined spectrofluorometrically with peritoneal mast cells. The monocyclic analogs in which the cysteine residues were replaced pairwise with alanine residues showed three-to ten-fold diminished histamine-releasing activity respectively, compared with the parent MCD peptide. Substantial increases in activity were observed where arginine residues were replaced by ornithines. The ornithine-mono substituted analog showed an almost six-fold increase and the ornithine-doubly substituted analog three-fold increase in histamine-releasing activity compared with the parent MCD peptide. The structural changes associated with these activities were followed by circular dichroism (CD) spectroscopy. Changes in the shape and ellipticity of the CD spectra reflected a role for the disulfide bonds and the two arginine residues in the overall conformation and biological activity of the molecule.

The CCK-2 receptor is located on the ECL cell, but not on the parietal cell

BACKGROUND

The interrelationship between histamine and gastrin in the physiological regulation of gastric acid secretion is still a matter of dispute. CCK-2 receptors are located on enterochromaffin-like (ECL) cells in corpus mucosa and gastrin stimulates acid production by releasing histamine from the ECL cells, which in turn stimulates the parietal cells. Whether parietal cells also possess gastrin receptors of physiological significance is unclear. The aim of the present study was to localize the CCK-2 receptor cellularly and concomitantly demonstrate a gastrin receptor response (histamine release).

METHODS

Fluorescein labelled cholecystokinin-8 (Fluo-CCK-8) was added to the arterial infusion to totally isolated, vascularly perfused rat stomachs to a final concentration of 130 pmol L(-1) for 1 min, either alone or along with 520 nmol(-1) CCK-8 after 10-min pre-perfusion with CCK-8. Immediately after the Fluo-CCK-8 had reached the oxyntic mucosa, biopsies were taken and the binding sites were localized by double immunohistochemistry combined with the tyramide signal amplification (TSA) technique. Venous histamine was measured before and during stimulation.

RESULTS

Fluo-CCK-8 (130 pM) evoked histamine release, and binding sites were found in the basal part of corpus mucosa, co-localized with histidine decarbocylase (HDC) immunoreactive ECL cells. No binding of Fluo-CCK was found in the mid-glandular region of corpus, dominated by parietal cells. Binding of Fluo-CCK-8 was abolished by concomitant perfusion with excess CCK-8.

CONCLUSION

Fluo-CCK-8 given to isolated rat stomachs in a physiological concentration binds to CCK-2 receptors on ECL cells and causes histamine release, whereas no binding of Fluo-CCK-8 to parietal cells was found.

Synthetic studies on glycosphingolipids from Protostomia phyla: synthesis of amphoteric glycolipid analogues containing a phosphocholine residue from the earthworm Pheretima hilgendorfi

Two kinds of amphoteric glycosphingolipid analogues from the earthworm Pheretima hilgendorfi were synthesized as follows: The key reaction is a coupling of a phosphocholine group at the position C-6 of 1 and 6 which was attempted using 2-chloro-2-oxo-1,3,2-dioxaphospholane, followed by reaction of the resulting cyclic phosphate intermediate with anhydrous trimethylamine to give 2 and 7. Subsequent debenzylation afforded target compounds (3, 8). Their ability to inhibit the histamine release in vitro was examined.

Histaminergic control of oxytocin release in the paraventricular nucleus during lactation in rats

The central neurotransmitters regulating both systemic and central release of oxytocin (OT) during lactation are not completely defined. Although central histaminergic systems have been implicated in systemic release of OT, the role of this neurotransmitter in suckling-induced intranuclear OT secretion has not been investigated. Therefore, microdialysis of the paraventricular nucleus (PVN) was used to determine if suckling stimulates histamine release within the PVN and if nursing-induced intranuclear OT release is reduced by local blockade of either H1 or H2 histamine receptors. Female Holtzman rats were implanted with microdialysis probes adjacent to the PVN on lactation days 8-12. The next day, the pups and dam were separated for 4 h, reunited, and again separated. Histamine concentrations in dialysates were measured before, during, and following suckling. In separate animals, a similar separation/reunion paradigm was used, but the dialysate OT concentration was measured during PVN perfusion with vehicle or an H1 or H2 receptor antagonist. Suckling increased dialysate concentrations of both histamine and OT in the PVN. Furthermore, local pharmacological blockade of either H1 or H2 receptors prevented the increase in OT release in the PVN during suckling. These data demonstrate that activation of histamine receptors in the PVN is necessary for intranuclear release of OT induced by suckling and extend previous findings demonstrating a similar relationship between central histamine and systemic release of OT.

PACAP stimulates gastric acid secretion in the rat by inducing histamine release

Previous studies have shown that pituitary adenylate cyclase-activating peptide (PACAP) stimulates enterochromaffin-like (ECL) cell histamine release, but its role in the regulation of gastric acid secretion is disputed. This work examines the effect of PACAP-38 on aminopyrine uptake in enriched rat parietal cells and on histamine release and acid secretion in the isolated vascularly perfused rat stomach and the role of PACAP in vagally (2-deoxyglucose) stimulated acid secretion in the awake rat. PACAP has no direct effect on the isolated parietal cell as assessed by aminopyrine uptake. PACAP induces a concentration-dependent histamine release and acid secretion in the isolated stomach, and its effect on histamine release is additive to gastrin. The histamine H2 antagonist ranitidine potently inhibits PACAP-stimulated acid secretion without affecting histamine release. Vagally stimulated acid secretion is partially inhibited by a PACAP antagonist. The results from the present study strongly suggest that PACAP plays an important role in the neurohumoral regulation of gastric acid secretion. Its effect seems to be mediated by the release of ECL cell histamine.

Antiallergic agents from natural sources. 3. Structures and inhibitory effects on nitric oxide production and histamine release of five novel polyacetylene glucosides from Bidens parviflora WILLD

Five new polyacetylene glucosides, bidensyneosides A1, A2, B, C (1-4), and 3-deoxybidensyneoside B (5), have been isolated from the air-dried whole plant of Bidens parviflora WILLD. The structures were identified based on spectroscopic analysis, physicochemical properties, and application of the modified Mosher method to be 3(R),8(E)-8-decene-4,6-diyne-1,3-diol 1-O-beta-D-glucopyranoside (1), deca-3(R),8(Z) 8-decene-4,6-diyne-1,3-diol 1-O-beta-D-glucopyranoside (2), 3(R)-deca-4,6,8-triyne-1,3-diol 1-O-beta-D-glucopyranoside (3), 3(R),8(E)-8-decene-4,6-diyne-1,3,10-triol 1-O-beta-D-glucopyranoside (4), and 8(E)-8-decene-4,6-diyne-1,10-diol 1-O-beta-D-glucopyranoside (5), respectively. These compounds inhibited nitric oxide (NO) production in lipopolysaccharide and interferon-gamma activated murine macrophages (RAW264.7) and also inhibited histamine release from rat mast cells stimulated by the antigen-antibody reaction.

Synthesis and physiological activity of novel tocopheryl glycosides

Vitamin E glycosides were synthesized and enzymatic hydrolysis was examined for use as potential pro-drugs, however, the glycoside bond was found to be stable. On the other hand, among the glycosides synthesized, dl-alpha-tocopherylglucoside (6b) and dl-alpha-tocopherylmannoside (6c) showed strong inhibitory action on histamine release from mast cells. In addition, 6c also showed a suppressive action on IgE antibody formation. Thus, tocopheryl glycoside showed new properties compared to tocopherol (vitamin E). In particular, 6c was shown to be a novel lead compound with excellent manifold anti-allergic activity and anti-inflammatory activity.

Mast cell degranulation and the role of T cell RANTES in oral lichen planus

OBJECTIVES

The present study investigated mast cell degranulation in oral lichen planus (OLP) and the effect of OLP lesional T cell supernatants on mast cell degranulation.

MATERIALS AND METHODS

Immunohistochemistry was used to identify mast cell degranulation in both OLP (n = 22) and normal control (n = 14) tissues. OLP lesional T cell lines (n = 5) and HMC-1 (a human leukemia mast cell line) were used to examine the effects of OLP T cell supernatants on mast cell degranulation in vitro.

RESULTS

Approximately 60% of mast cells were degranulated in OLP. OLP lesional T cells expressed mRNA for RANTES, and TNF-alpha stimulation upregulated OLP lesional T cell RANTES secretion. OLP lesional T cell supernatants induced degranulation of HMC-1 with release of TNF-alpha and histamine. Human recombinant RANTES similarly induced mast cell degranulation. Anti-RANTES antibody blocked OLP lesional T cell supernatant-induced mast cell degranulation.

CONCLUSIONS

This study is the first to show that OLP lesional T cells produce and secrete RANTES which triggers human mast cell degranulation. Degranulating mast cells release TNF-alpha which upregulates OLP lesional T cell RANTES secretion. Such a cyclical mechanism may underlie disease chronicity and future therapies may include blocking RANTES or TNF-alpha activity in OLP.

Cysteinyl-leukotriene release test (CAST) in the diagnosis of immediate drug reactions

BACKGROUND

The diagnosis of allergic reactions to drugs is difficult. Most skin tests are not standardized, and in vitro tests are needed to avoid provocation tests. Cross-linking of IgE on basophils is known to cause the release of both cysteinyl leukotriene (Cys-LT) and histamine. We aimed to evaluate the diagnostic utility (sensitivity, specificity, and efficiency) of measurement of sulfidoleukotrienes in drug allergy.

METHODS

We performed a prospective study in 55 patients with proven immediate adverse reactions to drugs (30 to beta-lactams, six to acetaminophen, and 19 to aspirin) and 64 drug-exposed nonallergic controls. Positive diagnosis was established by history, skin tests, and, if needed, oral provocation tests. Cys-LT release was determined after drug-allergen stimulation by the cellular antigen stimulation test (CAST(R)) technique. Histamine release was also assessed on the same samples by enzyme immunoassay. Spontaneous and anti-FcepsilonRIalpha-induced mediator release was also studied in all subjects. Sensitivity, specificity, and efficiency were calculated.

RESULTS

Net Cys-LT release was over the maximal threshold given by the manufacturer in 19/55 patients and in 9/64 controls. Net histamine release was over 5% of total histamine content in 28/55 patients and 34/64 controls. The efficiency of both tests was low.

CONCLUSION

Thus, in most cases, the in vitro Cys-LT test has little or no diagnostic utility and is not superior to histamine release.

Fusarium solani major allergen peptide IV-1 binds IgE but does not release histamine

BACKGROUND

Fusarium solani (FS) is an important allergen source afflicting 4% of the nasobronchial allergy patients. Fus s I3596*, a 65 kDa major glycoprotein allergen of FS reacts with 95% fungus sensitive patients.

OBJECTIVES

To purify and characterize a potent peptide from Fus s I3596* which may be useful for therapeutic purposes.

METHODS

The 65 kDa protein was sequentially cleaved with trypsin and cyanogen bromide (CNBr). The cleaved products were purified on reverse phase high performance liquid chromatography (rpHPLC) column and functionally characterized by in vitro and in vivo methods for its IgE binding and histamine release.

RESULTS

The protein on cleavage showed 11 peaks (I to XI). Of these, peaks I, III, IV and V were highly allergenic as determined by IgE ELISA. These peaks were further purified and peptide IV-1 was most potent in comparison to other peptides by ELISA-inhibition. This peptide showed IgE binding but could not evoke intradermal response in Fusarium-sensitive patients. Heparinized blood challenged with peptide IV-1 does not release histamine. Preincubation of heparinized blood with peptide IV-1 and challenging with crude extract blocked histamine release in a dose dependent manner.

CONCLUSION

Peptide IV-1 binds to IgE but does not release histamine, demonstrating its potential use in therapy of Fusarium-allergic patients.

Mast cells are involved in the gastric hyperemic response to acid back diffusion via release of histamine

Acid back diffusion into the rat stomach mucosa leads to gastric vasodilation. We hypothesized that histamine, if released from the rat mucosa under such conditions, is mast cell derived and involved in the vasodilator response. Gastric blood flow (GBF) and luminal histamine were measured in an ex vivo chamber. Venous histamine was measured from totally isolated stomachs. Mucosal mast cells (MMC), submucosal connective tissue mast cells (CTMC), and chromogranin A-immunoreactive cells (CgA IR) were assessed morphometrically. After mucosal exposure to 1.5 M NaCl, the mucosa was subjected to saline at pH 5.5 (control) or pH 1.0 (H(+) back diffusion) for 60 min. H(+) back diffusion evoked a marked gastric hyperemia, increase of luminal and venous histamine, and decreased numbers of MMC and CTMC. CgA IR cells were not influenced. Depletion of mast cells with dexamethasone abolished (and stabilization of mast cells with ketotifen attenuated) both hyperemia and histamine release in response to H(+) back diffusion. GBF responses to H(+) back diffusion were attenuated by H(1) and abolished by H(3) but not H(2) receptor blockers. Our data conform to the idea that mast cells are involved in the gastric hyperemic response to acid back diffusion via release of histamine.

Neuronal histamine release elicited by hyperthermia mediates tracheal dilation and pressor response

Whether brain histaminergic neurons contribute to the regulation of tracheal tone and peripheral vascular tone under hyperthermia was investigated in anesthetized rabbits. Histamine release from the rostral ventrolateral medulla (RVLM), the raphe nuclei, and the solitary nucleus of the medulla oblongata was significantly increased by hyperthermia. The increased histamine was significantly suppressed by 10−6 M tetrodotoxin microdialyzed in each area. Tracheal pressure and mean arterial pressure were significantly decreased and increased by hyperthermia, respectively. An H1-receptor antagonist, 5 × 10−6 M (+)-chlorpheniramine, bilaterally microdialyzed in the RVLM significantly enhanced histamine release in the RVLM as well as significantly suppressed tracheal dilation and pressor response caused by hyperthermia. These data indicate that histamine release in the medulla oblongata is enhanced by hyperthermia. The enhanced histamine is the neuronal origin and the cause of tracheal dilation and pressor response at least via H1 receptors in the RVLM. Brain histaminergic neurons play important roles in tracheal tone and peripheral vascular tone via H1 receptors in the RVLM and homeostasis on body temperature.

D-galactose-specific sea urchin lectin sugar-specifically inhibited histamine release induced by datura stramonium agglutinin: differences between sugar-specific effects of sea urchin lectin and those of D-galactose- or L-fucose-specific plant lectins

A new sea urchin lectin from Toxopneustes pileolus, is D(+)galactose (Gal)-, D(+)fucose (Fuc)-specific. Incubation of rat peritoneal mast cells with the lectin in the presence of 0.3 mM CaCl2 for 10 min significantly and dose-dependently inhibited the histamine release induced by N-acetyl glucosamine (GlcNAc)-specific Datura stramonium agglutinin (DSA), an activator of the Gi-protein-dependent pathway in mast cells. This inhibition by the sea urchin lectin was sugar-specifically reversed in the presence of D(+)Gal or D(+)Fuc but not L(-)Fuc. The sea urchin lectin had no effect on the histamine release induced by compound 48/80, slightly inhibited the histamine release induced by substance P and mastoparan, and slightly enhanced the histamine release induced by melittin, but these effects were not dose-dependent. Compound 48/80, substance P, mastoparan and melittin are mast cell activators without sugar residues. It is suggested that the lectin binds to D(+)Gal residues of DSA to interfere with mast cell activation induced by DSA, a glycoprotein with arabinose and Gal residues. The effects of plant lectins with affinity to D(+)Gal, N-acetyl galactosamine and/or sialic acid and L(-)Fuc on the histamine release induced by DSA, compound 48/80 and substance P were also examined.

Can conditioned histamine release occur under urethane anesthesia in guinea pigs?

Many clinical and experimental data have shown that learning can occur under general anesthesia. To clarify this possibility with respect to allergic reactions, particularly asthmatic responses, we first established classical conditioned histamine release in response to a neutral odor by using pairings of the odor and an inhaled antigen for five sessions (Experiment 1) and then investigated whether conditioned histamine release into the plasma, bronchoalveolar lavage fluid (BALF), and lung tissue, which followed such a conditioning procedure, would be produced in urethane-anesthetized guinea pigs in the presence or absence of antigen (Experiment 2). Ovalbumin (OA) was used as the unconditioned stimulus (US) and dimethylsulfide (DMS) served as the conditioned stimulus (CS) in both experiments. In Experiment 1, the plasma histamine levels in the conditioned group increased significantly more than those of the unpaired control group in response to the CS during consciousness. In Experiment 2 in the absence of antigen, however, no significant differences in the histamine levels were found regarding the groups (DMS, triethylamine, saline, or unsensitized) or the time course (before, immediately, 5 min, and 10 min after the inhalations) during anesthesia, except for the finding that the histamine levels in the lung tissue specimens from the DMS group were significantly higher than those from the triethylamine group. In Experiment 2 in the presence of antigen, there was a significant increase in the plasma histamine levels after exposure to the US, irrespective of the presence of the CS, however, no significant difference in the histamine levels was observed between the US and the CS+US groups. These results indicated that a classically CS might not induce asthmatic responses under anesthesia.

The activation of synovial mast cells: modulation of histamine release by tryptase and chymase and their inhibitors

Mast cells have been implicated as having pivotal roles in arthritis, but little is known of the processes leading to the activation of synovial mast cells or their potential for pharmacological control. We have investigated the ability of tryptase and chymase, and inhibitors of these major mast cell proteases to modulate the activation of mast cells from human synovial tissue. The tryptase inhibitor drug N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride (APC366) inhibited immunoglobulin E (IgE)-dependent histamine release in a dose-dependent manner, with about 70% inhibition being achieved at a dose of 300 microM. Histamine release stimulated by calcium ionophore A23187 was also inhibited by this compound. The chymase inhibitor chymostatin inhibited IgE-dependent histamine release by approximately 60% at 1 microg/ml. Tryptase at concentrations of 3.0 microg/ml and greater stimulated histamine release from synovial cells, which was dependent on catalytic activity, whereas chymase had little effect on these cells. The activation of mast cells by tryptase may represent an amplification process in the synovium. The mast cell stabilising properties of inhibitors of tryptase and chymase could be of therapeutic value in arthritis.

Effect of ovarian hormones on intestinal mast cell reactivity to substance P

Evidence exists to support the concept that ovarian hormones influence mast cell functioning and related events. Here, we evaluated the constitutive gender difference and the influence of ovarian status on rat mast cell (MC) distribution in jejunum and colon, histamine synthesis and/or its release elicited by Substance P (SP). Higher mast cell (MC) number and histamine release were found in female compared with male. In female rats, hormonal status did not affect the density of resident MC neither in the jejunum nor in the colon. Interestingly, histamine levels released after SP stimulation of jejunal segment was reduced in ovariectomized (OVX) compared with sham OVX rats, and restored in OVX female receiving progesterone. In the colon, OVX resulted in a significant increase in histamine levels released after SP stimulation and a treatment with progesterone did not restore basal histamine levels. Thus, ovarian steroid hormones do not affect jejunal and colonic mast cell number. However, the hormonal status differently influences jejunal and colonic MC sensitivity to SP.

Vascular permeability in allergic conjunctivitis in mice lacking histamine H1 receptors

To clarify the role of histamine H1 receptors in allergic conjunctivitis, changes in vascular permeability of the conjunctiva were measured in histamine H1 receptor deficient mice. Wild-type mice showed a significant increase in vascular permeability of the conjunctiva induced by histamine. However, no such increase was found in histamine H1 receptor deficient mice. On the other hand, no differences were observed between wild-type and histamine H1 receptor deficient mice in response to serotonin. A significant increase in vascular permeability was observed in actively sensitized wild-type mice, whereas no increase was observed in histamine H1 receptor deficient mice. Similar findings were noted in passively sensitized animals. Histamine contents of the conjunctiva were significantly decreased by topical application of antigen in both wild-type and histamine H1 receptor deficient mice after active sensitization with antigen. These findings suggested that vascular permeability in the conjunctiva in allergic conjunctivitis is entirely regulated through histamine H1 receptor.

Intradermal application of nociceptin increases vascular permeability in rats: the possible involvement of histamine release from mast cells

Intradermal application of nociceptin was used to investigate its in vivo effect on the inflammatory response in rats. Intradermal nociceptin (5 pmol/site-5 nmol/site) increased vascular permeability in a dose-dependent manner. The increased vascular permeability by nociceptin (5 nmol/site) was dose-dependently inhibited by the histamine H1 receptor antagonist pyrilamine (50 pmol/site-5 nmol/site). In rat peritoneal mast-cell preparation, nociceptin (10(-8)-10(-4) M) dose-dependently stimulated histamine release. The effect of nociceptin (10(-5) M) occurred rapidly (within 30 s) and was inhibited by pertussis toxin, Ca2+, but was not sensitive to naloxone, a classical opioid receptor antagonist. These characteristics are in agreement with features of the opioid-receptor-like 1 (ORL1) receptor, a non-classical opioid receptor linked to a pertussis toxin-sensitive G protein. Taken together, these data suggest that nociceptin, likely acting via the ORL1 receptor at the site of inflammation, might be critical for the enhancement of the inflammatory response by stimulating histamine release from mast cells.