IL-18 mediates the formation of stress-induced, histamine-dependent gastric lesions

A role of IL-18 in the induction of gastric lesions by water immersion and restraint stress (WRS) was investigated. When wild-type BALB/c mice were exposed to WRS, levels of IL-18 in the serum and stomach increased rapidly with the development of acute gastric lesions. In IL-18-deficient mice [IL-18 knockout (KO) mice] similarly exposed to WRS, no gastric lesions were observed, but the administration of IL-18 before exposure to WRS resulted in the induction of WRS-induced gastric lesions. WRS enhanced gastric histidine decarboxylase (HDC) activity with concomitant increases in gastric histamine content. In IL-18 KO mice, the WRS-induced elevation of gastric HDC activity and histamine levels was much less than that in wild-type mice, but it was augmented by prior administration of IL-18. Treatment of wild-type mice with cimetidine, a histamine H2 receptor antagonist, inhibited the formation of WRS-induced gastric lesions with no effect on the induction of gastric IL-18 by WRS. Levels of corticosterone, one of the stress indicators, were lower in IL-18 KO mice than in wild-type mice. The glucocorticoid receptor antagonist mifepristone had no effect on gastric IL-18 and histamine levels but aggravated the stress-induced gastric lesions, indicating that corticosterone was not involved in the IL-18-mediated formation of stress-induced gastric lesions. These results indicate that IL-18 is involved in the induction of gastric lesions by WRS through augmentation of HDC activity and production of histamine in the stomach.

Adventitial inflammation: a possible pathogenic link to the instability of atherosclerotic plaque

A variety of cells, including fibroblasts, mast cells, macrophages, and ganglionic cells, are present in coronary artery adventitia. In the infarct-related coronary arteries of myocardial infarction patients, the majority of mast cells are found in the outer layer of the adventitia. Neurogenic stimulation of mast cells in the adventitia of coronary arteries may release vasoactive compounds, such as histamine and leukotrienes, which can contribute to the complex neurohormonal response that leads to abnormal coronary vasoconstriction. Lymphocytes and bacteria are also present mainly in the adventitial layer. Chlamydia pneumoniae is directly involved in the development of adventitial and plaque inflammation (pan-arteritis), leading to plaque rupture. Adventitial O(2)(-) may also play an extensive role in the control of vascular tone. Therefore, adventitial inflammation may play a pivotal role for atherosclerotic lesion development and atheroma instability.

Immunological activation of human umbilical cord blood mast cells induces tryptase secretion and interleukin-6, and histidine decarboxilase mRNA gene expression

Allergy is the result of a complex immune cascade leading to the disregulated production of Th2 cytokines, the generation of allergen-specific IgE-producing B cells and the subsequent activation and degranulation of mast cells upon allergen challenge. Mast cell effector function significantly influences the quantity, duration and magnitude of most allergic reactions. Here, using isolated human umbilical cord blood mast cells (HUCBMC) from CD34+ cells, activated with anti-IgE (10 microg/ml) in culture, we found an augmented release of IL-6, tryptase and histamine (p < 0.01 compared with control). In addition, in these cells anti-IgE (10 microg/ml) activated the expression of histidine decarboxylase (HDC) and IL-6. In these studies we describe a new biological activity of anti-IgE in inducing histidine decarboxylase and IL-6, suggesting that this cytokine may have an important effect on allergic and inflammatory diseases mediated by mast cells. Moreover, with these data we confirm the immunoregulatory and inflammatory function of mast cells.

Two neolignan glucosides and antihistamine release activities from Bidens parviflora WILLD

Two new neolignan glucosides, bidenlignasides A (1) and B (2), were isolated from the whole plant of Bidens parviflora WILLD. The structures of the two new compounds 1 and 2 established to be 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-3-[5E-(3-hydroxypropenyl)-3-methoxy-2-O-beta-D-glucosyl)phenyl] propan-1-one and 3-{3-[1,3-dihydroxy-3-(4-hydroxy-3-methoxyphenyl)propyl]-4-hydroxy-5-methoxyphenyl}-allyl-O-beta-D-glucuside, respectively, on the basis of spectral and chemical evidence. Compounds 1 and 2 were found to inhibit histamine release from peritoneal exudate mast cells induced by antigen-antibody reaction.

Cardiac anaphylaxis: pathophysiology and therapeutic perspectives

Cardiac anaphylaxis refers to the functional and metabolic changes in the heart caused by the anaphylactic release of histamine and vasoactive products of arachidonic acid cascade by mast cells and basophils. As in most type I hypersensitivity-based diseases, histamine plays a key role in the pathophysiology of cardiac anaphylaxis. In the heart, mast cell activation and histamine release are controlled by multiple endogenous mechanisms, including adrenergic neural control, histamine-dependent negative feedback operated through H2 receptors, and the endogenous generation of nitric oxide (NO) and carbon monoxide (CO). All these mechanisms can be targeted by substances that have revealed a clear-cut effect in blunting cardiac anaphylaxis in experimental animal models, and could be developed as potential, novel anti-anaphylactic drugs. In this article, we discuss new findings and significant trends related to this topic.

Attenuation of human lung mast cell degranulation by bronchial epithelium

BACKGROUND

Human lung mast cells (HLMC) lie in close proximity to the bronchial epithelium in asthma and adhere with high affinity to bronchial epithelial monolayers in vitro. We investigated the consequences of this adhesive interaction on HLMC activation in response to Fc epsilon RI cross-linking.

METHODS

Human lung mast cells were cultured with the bronchial epithelial cell line BEAS-2B or plastic control for either 30 min or 16 h and then activated with anti-IgE. Histamine was measured by radioenzymatic assay.

RESULTS

After co-culture for 30 min, IgE-dependent histamine release from HLMC was identical on both BEAS-2B and plastic. After 16 h of co-culture, there was a marked decrease in constitutive and IgE-dependent histamine release from HLMC cultured on BEAS-2B compared with those cultured on plastic or fibronectin. In contrast, the Ca(2+)/ATPase inhibitor thapsigargin produced concentration-dependent histamine release that was significantly increased on BEAS-2B compared with plastic. IgE-dependent degranulation was not significantly affected by BEAS-2B-conditioned medium.

CONCLUSIONS

BEAS-2B bronchial epithelial cells attenuate IgE-dependent but not thapsigargin-induced histamine release from HLMC. The differential effect with anti-IgE compared with thapsigargin suggests that the mechanism includes interference with the proximal Fc epsilon RI signalling pathway.

Are basophil histamine release and high affinity IgE receptor expression involved in asymptomatic skin sensitization?

BACKGROUND

Immunoglobulin (Ig)E-sensitized persons with positive skin prick test, but no allergy symptoms, are classified as being asymptomatic skin sensitized (AS). The allergic type 1 disease is dependant on IgE binding to the high affinity IgE-receptor (FcepsilonRI) expressed on basophils and mast cells. However, a relationship between the AS status and FcepsilonRI has not been investigated. We aimed to characterize basophils from AS by looking at histamine release (HR) (sensitivity and reactivity) and the FcepsilonRI molecule, and compare it with nonatopic (NA) or allergic (A) persons.

METHODS

Blood was obtained from NA (n = 14), grass and/or birch A persons (n = 17) and mono-sensitized grass or birch pollen AS (n = 12). The basophil sensitivity and reactivity were examined by anti-IgE triggered HR. Surface expression of FcepsilonRI and IgE were measured by flow cytometry, FcepsilonRIalpha protein was identified using a radioimmunoassay and Western blot. mRNA coding for the classic FcepsilonRIbeta-chain and the truncated form (FcepsilonRIbetaT) were determined by real-time PCR.

RESULTS

The AS group was less reactive than NA or A persons when triggered by anti-IgE and had a significant higher number of nonresponders. However, there was no difference in sensitivity among the three groups and furthermore; the groups did not vary in FcepsilonRI- and IgE-surface expression, FcepsilonRIalpha-protein level or beta/betaT ratio.

CONCLUSION

Basophils from AS persons are less reactive and include more nonresponders than basophils from NA and A persons, but do not differ regarding the FcepsilonRI molecule.

Chronic urticaria: pathophysiology and etiology, or the what and why

Chronic urticaria (CU) is a relatively common but vexing disease. The pathophysiology is based on the cutaneous mast cell release of mediators, predominantly histamine. Release can be induced via specific immunoglobulin E (IgE), components of complement activation and nonspecifically by various compounds including endogenous peptides, endorphins, and enkephalins. In >30% of CU patients, autoimmune phenomena have been found, characterized by positive autologous serum skin test, antibodies to the alpha-subunit of the basophil IgE receptor, to IgE itself, and, perhaps, the most clinically relevant, thyroid autoimmunity. Studies suggest that the products of the activated immune system can lower the cutaneous mast cell release threshold, possibly allowing activation by endogenous compounds. The resulting release of mediators produces the clinical picture of recurrent hives. Although the goal of management of CU is the identification of a treatable cause, in most CU patients, especially adults, a cause is not frequently found. Identified causes include drugs, foods, infections, immune complex production leading to urticarial vasculitis, autoantibody production, and underlying autoimmune disease, particularly autoimmune thyroiditis. The treatment of the thyroiditis with suppressive doses of thyroid hormone often results in the remission of the CU. Given the marginally effective and sometimes dangerous medical therapy available for CU, a systematic and thorough approach to identify a treatable cause in difficult CU patients is warranted.

[Effect of nociceptin on histamine and serotonin release in the central nervous system]

Role in pain sensation of both nociceptin (NC), the bioactive heptadecapeptide sequence of preproorphaninFQ and of histamine has been widely evidenced in the central nervous system (CNS). In the current series of experiments effect of intracerebroventricularly (i.c.v.) administered NC (5.5 nmol/rat) on histamine and serotonin levels in blood plasma, CSF and brain areas (hypothalamus and hippocampus) was studies and compared to the effect of the mast cell degranulator Compound 48/80(100microg/kg, i.c.v.) and the neuroactive peptide Substance P (50nmol/rat, i.c.v.). It was found that all the three compounds increased the histamine level in the CNS, however their activity concerning the mast cell-, and neuronal histamine release is different. NC could release histamine from both the mast cells and the neurons and it decreased CNS serotonin levels. Substance P was found the most potent in increasing CNS histamine levels. Compound 48/80 treatment resulted in elevated histamine levels both in the CNS and blood plasma. It is concluded that the histamine releasing effects of i.c.v. administered NC and SP are limited to the CNS, but in the effect of Compound 48/80 its blood-brain barrier impairing activity is also involved. Data also demonstrate that NC has significant effect on both the histaminergic and serotonergic neurotransmission in the CNS.

Effect of interleukin-8 on histamine release from totally isolated vascularly perfused rat stomach

BACKGROUND

Recent studies have demonstrated relationships between cytokines and gastric acid secretion. The present study was performed in rats to elucidate the effects of interleukin-8 (IL-8) on gastric acid secretion through an increase in histamine release from the stomach.

METHODS

The experiments were performed in gastric lumen-perfused rats for the study of acid secretion and in totally isolated vascularly perfused rat stomach preparations for the study of histamine release. The histamine in the effluent was determined by radioimmunoassay.

RESULTS

IL-8 (500 ng) significantly enhanced gastrin-stimulated acid secretion. IL-8, at a concentration of 500 ng/20 ml per 10 min, did not alter basal histamine release, but at 100 ng/20 ml and 500 ng/20 ml it dose-dependently increased gastrin-stimulated histamine release.

CONCLUSIONS

IL-8 enhances gastrin-stimulated acid secretion and histamine release from the rat stomach, which may explain the enhancing effect of IL-8 on gastric acid secretion.

Kassinakinin S: A novel histamine-releasing heptadecapeptide from frog (Kassina senegalensis) skin secretion

Amphibian defensive skin secretions remain a largely untapped resource for the peptide biochemist with an interest in the identification, structural characterization, and precursor cDNA cloning of novel bioactive peptides. Here we report the isolation, structural characterization, functional profiling, and nucleotide sequence of precursor cDNA of a novel histamine-releasing heptadecapeptide, FIPVTLLALHKIKEKLN-amide, from the defensive skin secretion of the African running frog, Kassina senegalensis. This peptide was found to be a potent histamine secretagogue (EC(50) = 6 microM; maximal release = 25 microM) in a rat peritoneal mast cell model system and was accordingly named kassinakinin S. The open-reading frame of the cDNA encoding prepro-kassinakinin S was found to consist of 71 amino acid residues containing a single copy of kassinakinin S and its glycyl residue amide donor at the C-terminus. Kassinakinin S can thus be added to the growing list of amphibian skin bioactive peptide prototypes.

Food hypersensitivity-immunologic (peripheral) or cognitive (central) sensitisation?

Patients with food hypersensitivity suffer poor quality of life and several unexplained health complaints, both abdominal and extra-abdominal. Part of the suffering is due to healthcare providers' neglect and poor insight, allowing a strong position for alternative medicine. Distinguishing food allergy from functional and organic disorders can be extremely difficult. We have found examination of faecal calprotectin and gut permeability to be useful for excluding organic disease, whilst conventional provocation tests for positive diagnosis of food hypersensitivity are cumbersome. Our new ultrasound provocation test has been promising, but we acknowledge that much work remains to be done before its sensitivity and specificity can be finally established. The majority of patients with self-reported food hypersensitivity have a non-allergic hypersensitivity disorder. We suggest that cognitive-emotional sensitisation at the brain level, and not peripheral (immunological) sensitisation, is a major pathogenetic mechanism by which the patients' various abdominal and extra-abdominal health complaints are generated. Extensive activation of cognitive networks might be triggered by peripheral sensory mechanisms, often misinterpreted as 'food allergy'. Clearly, the approach to patients with food hypersensitivity should be interdisciplinary.

Organic cation transporter 3 modulates murine basophil functions by controlling intracellular histamine levels

In this study, we identify the bidirectional organic cation transporter 3 (OCT3/Slc22a3) as the molecule responsible for histamine uptake by murine basophils. We demonstrate that OCT3 participates in the control of basophil functions because exogenous histamine can inhibit its own synthesis--and that of interleukin (IL)-4, IL-6, and IL-13--through this means of transport. Furthermore, ligands of H3/H4 histamine receptors or OCT3 inhibit histamine uptake, and outward transport of newly synthesized histamine. By doing so, they increase the histamine content of basophils, which explains why they mimic the effect of exogenous histamine. These drugs were no longer effective in histamine-free histidine decarboxylase (HDC)-deficient mice, in contrast with histamine itself. Histamine was not taken up and lost its inhibitory effect in mice deficient for OCT3, which proved its specific involvement. Intracellular histamine levels were increased strongly in IL-3-induced OCT3-/- bone marrow basophils, and explained why they generated fewer cytokines than their wild-type counterpart. Their production was enhanced when histamine synthesis was blocked by the specific HDC inhibitor alpha-fluoro-methyl histidine, and underscored the determinant role of histamine in the inhibitory effect. We postulate that pharmacologic modulation of histamine transport might become instrumental in the control of basophil functions during allergic diseases.

Mast cell activation is differentially affected by heat shock

OBJECTIVE

Mast cells play pivotal roles in immediate-type and inflammatory allergic and nonallergic reactions. Cross-linking of the high-affinity receptor for IgE (FcepsilonRI) on mast cells activates a signaling pathway leading to Ca2+ mobilization and is followed by degranulation and the release of histamine and other preformed mediators, as well as de novo synthesis of arachidonic acid metabolites. In a previous study, we have demonstrated that heat shock activates heat shock transcription factor-1 (HSF-1), induces heat shock protein 70 (HSP70), and suppresses cytokine production in bone marrow-derived mast cells (BMMC). In this study, we further investigated the effects of heat shock on the activation of mast cells and the release of mast cell mediators.

METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-)mice, responsiveness to heat shock was monitored by measuring beta-hexosaminidase and leukotriene C4 (LTC4) release.

RESULTS

Using BMMC, we found that heat shock inhibits degranulation of BMMC without affecting leukotriene production. To further elucidate the mechanism of suppression of degranulation, we studied the effects of heat shock on the regulation of signal transduction in more detail. We found that heat shock inhibits calcium mobilization and tyrosine phosphorylation of Syk and SHIP upon IgE receptor activation, but increases the phosphorylation of SHP-1 and -2. Moreover, our results revealed that suppression of tyrosine phosphorylation of Syk and SHIP coincided with an increased tyrosine phosphatase activity.

CONCLUSION

The inhibitory action of heat shock toward mast cell degranulation is likely due to shifting the balance between kinase and phosphatase activity.

Comparison of antigen-induced leukotriene and histamine release from nasal scrapings in allergic rhinitis

BACKGROUND

In the early phase response of allergic rhinitis, the nasal mucosa produces important mediators including histamine and leukotrienes.

OBJECTIVE

To investigate the relationship between antigen-induced leukotriene release and histamine secretion in nasal scrapings.

METHODS

Using nasal mucosal scrapings from patients sensitized to only house dust mite, we studied the time course of antigen-induced leukotriene release and its relationship to histamine release.

RESULTS

Cumulative peptydyl leukotriene (LT) production from nasal scrapings increased from 10 min to approximately 90 min following exposure to mite antigen. The rate of LT release was small (<5 pg/10 min) until 10 min following antigen exposure, increased to approximately 250 to 350 pg LT/10 min from 10 to 45 min post exposure, was reduced to <100 pg/10 min by 60 to 150 min, and by 180 min LT production was negligible. By contrast, histamine secretion began 30 sec after antigen exposure and was complete within approximately 10 min. Net antigen-induced LT secretion strongly correlated (R=0.72) with net antigen induced histamine secretion with a ratio of 1:8.7. In addition, net LT/ng histamine and total LT secretion correlated well with antigen-specific IgE in serum, and with the patients' symptoms.

CONCLUSION

There is a close relationship between amounts of histamine and LT secretion from antigen challenged nasal mucosa, although the time course of LT release is delayed. In the early phase response, LT are likely to be generated from mucosal mast cells, and thus, mast cell activation will provide an important therapeutic target.

Effect of oxygen-glucose deprivation on degranulation and histamine release of mast cells

The purpose of this study was to investigate the effect of oxygen-glucose deprivation (OGD) on degranulation and histamine release of mast cells. Cultured mast cells were exposed to OGD for 1, 2, 4, 8, or 16 h. At 2 h of OGD exposure, the degranulation percentage of mast cells had increased and subsequently showed a progressive further increase, associated with a similar change in lactate dehydrogenase release. Histamine release increased significantly from 1 h of OGD exposure. These results indicate that OGD induces mast cells to degranulate, possibly via a cytotoxic response. This in vitro ischemic model of mast cells might clarify their roles in the pathological processes induced by cerebral ischemia.

Modulation of gastric hemorrhage and ulceration by oxidative stress and histamine release in Salmonella typhimurium-infected rats

Infection with Salmonella typhimurium can produce multiple organ dysfunctions. However, document concerning with gastric hemorrhagic ulcers occur in this infectious disease is lacking. The aim was to study modulation of gastric hemorrhagic ulcer by oxidative stress and mast cell histamine in S. typhimurium-infected rats. Additionally, the protective effects of drugs, such as ofloxacin, lysozyme chloride, ketotifen, ranitidine, and several antioxidants, including exogenous glutathione (GSH), allopurinol and dimethylsulfoxide (DMSO) were evaluated. Male Wistar rats were injected intrajejunally with a live culture of S. typhimurium (1 x 10(10) colony-forming units/rat) and followed by deprivation of food for 36 h. Age-matched control rats received sterilized vehicle only. Rat stomachs were irrigated for 3 h with either normal saline or a simulated gastric juice containing 100 mM HCl, 17.4 mM pepsin and 54 mM NaCl. S. typhimurium caused aggravation of offensive factors, including enhancing gastric acid back-diffusion, mucosal lipid peroxide generation, histamine release, microvascular permeability and hemorrhagic ulcer, as well as an attenuation of defensive substances, such as mucosal GSH and mucus level. Intragastric irrigation of gastric juice caused further aggravation of these gastric biochemical parameters. This exacerbation of ulcerogenic factors was abolished by pretreatment of ofloxacin and lysozyme chloride. Antioxidants, such as reduced GSH, allopurinol and DMSO also produced significant (P < 0.05) amelioration of gastric damage in S. typhimurium infected rats. In conclusion, gastric oxidative stress and histamine play pivotal roles in the formation of hemorrhagic ulcers that were effectively ameliorated by ofloxacin, lysozyme chloride, ketotifen, ranitidine, diamine oxidase and various antioxidants in S. typhimurium-infected rats.

Phenotypic profiling of engineered mouse melanomas with manipulated histamine production identifies histamine H2 receptor and rho-C as histamine-regulated melanoma progression markers

In the present study, the impact of acquired neoplastic L-histidine decarboxylase (HDC) expression, and its direct consequence, the release of histamine in the tumor environment, was assessed on melanoma tumor progression. B16-F10 mouse melanoma cells were manipulated via stable transfection, and nine novel transgenic variants were generated in triplicates, constitutively expressing the full-length sense mouse HDC mRNA, a mock control, and an antisense HDC RNA segment, respectively. Establishing both primary skin tumors and lung metastases in C57BL/6 mice, the nine variants with different histamine-releasing capacities were subjected to a comprehensive comparative progression profiling in vivo. Our analyses showed trends of markedly accelerated tumor growth (P < 0.001), and moderately increased metastatic colony-forming potential (P = 0.010) along with rising levels of local histamine production. Using RNase protection assay for screening of the melanoma progression profile, and Western blotting for subsequent result validation, we looked for molecular progression markers affected by melanoma histamine secretion. Investigation of 21 functionally clustered markers associated with tumor proliferation, angiogenesis, invasivity, metastasis formation, local or systemic immunomodulation, and histamine signaling revealed positive correlations between histamine production, tumor histamine H2 receptor and rho-C expression (P < 0.001, P = 0.002, respectively). These observations confirm the involvement of histamine in the molecular machinery of melanoma progression.

Effect of Lo Han Kuo (Siraitia grosvenori Swingle) on nasal rubbing and scratching behavior in ICR mice

We studied the effect of Lo Han Kuo (Siraitia grosvenori Swingle) on histamine-induced nasal rubbing and compound 48/80-induced skin scratching behavior in ICR mice. An extract and glycoside (a complex of sweet components) of Lo Han Kuo were used in the study. Both the extract and glycoside caused no significant effect on nasal rubbing or scratching behavior, even at a dose of 1000 mg/kg when administered in a single dose. However, the effect of Lo Han Kuo became clear after repeated administration, and 300 and 1000 mg/kg of both extract and glycoside significantly inhibited nasal rubbing and skin scratching behavior after consecutive treatment for 4 weeks. Both the extract and glycoside inhibited the histamine release induced by compound 48/80 at concentrations of 300 and 1000 microg/ml. From these results, it is assumed that the inhibition of nasal rubbing and skin scratching behavior induced by Lo Han Kuo occurs through a mast cell-dependent mechanism.

Evidence for a restricted rather than generalized stimulatory response of skin-derived human mast cells to substance P

To resolve the controversy regarding substance P (SP) mediated stimulation of mast cells (MC), we demonstrate that SP triggers histamine release from purified human skin MC (sMC), but contrast to stimulation via FcepsilonRI, does not effect the production of TNF-alpha or IL-8. Conversely, both anti-IgE and SP are suppressive in terms of IL-6. By quantitative RT-PCR, the amount of templates at baseline (per 25 ng total RNA) is 2178 (IL-6), 2,665 (IL-8) and 94 (TNF-alpha), and remains unaltered by SP. Contrast to sMC, LAD2 MC respond to SP with stronger histamine release and robust TNF-alpha production in an only partially neurokinin-1R mediated manner, while histamine release of sMC is chiefly mediated by this receptor. We conclude that human sMC are responsive to SP in a selective manner by eliciting degranulation without the induction of cytokines and that SP-triggered cytokine production varies among MC subtypes, likely through differences in signaling mechanisms.

The vagus regulates histamine mobilization from rat stomach ECL cells by controlling their sensitivity to gastrin

The ECL cells in the oxyntic mucosa secrete histamine in response to gastrin, stimulating parietal cells to produce acid. Do they also operate under nervous control? The present study examines histamine mobilization from rat stomach ECL cells in situ in response to acute vagal excitation and to food or gastrin following vagal or sympathetic denervation. Applying the technique of microdialysis, we monitored the release of histamine by radioimmunoassay. Microdialysis probes were placed in the submucosa on either side of the stomach, 3 days before experiments. The rats were awake during microdialysis except when subjected to electrical vagal stimulation. One-sided electrical vagal stimulation raised serum gastrin and mobilized gastric histamine. However, gastrin receptor blockade prevented the histamine mobilization, indicating that circulating gastrin accounts for the response. Vagal excitation by hypoglycaemia (insulin) or pylorus ligation did not mobilize either gastrin or histamine. The histamine response to food was almost abolished by gastrin receptor blockade, and it was halved on the denervated side after unilateral subdiaphragmatic vagotomy. While the histamine response to a near-maximally effective dose of gastrin was unaffected by vagotomy, the response to low gastrin doses was reduced significantly. Abdominal ganglionic sympathectomy failed to affect the histamine response to either food or gastrin. In conclusion, gastrin is responsible for most of the food-evoked mobilization of ECL-cell histamine. The histamine response to electrical vagal stimulation reflects the effect of circulating gastrin rather than a direct action of the vagus on the ECL cells. Vagal denervation was accompanied by an impaired histamine response to food intake, probably reflecting the right-ward shift of the serum gastrin concentration-histamine response curve. The results suggest that the vagus controls the sensitivity of the ECL cells to gastrin.