Plasma Histamine Concentrations Research Articles

DIETARY EFFECTS OF MAGNESIUM ON HISTAMINE METABOLISM AND URINE ACIDITY IN DOMESTIC FELINES

Magnesium deficiency has been associated with increased histamine production in rats. Limitation of Mg with acidifying foods is common practice for management of urinary tract health in domestic cats. Nine healthy adult female shorthair cats were used in a 3 period random crossover experiment with fixed treatment sequences to test the effects of dietary Mg (0.06, 0.12 and 0.18% DM) on histamine in blood and urine. The dry-extruded test foods were fed in sufficient amounts to maintain ideal body weight and obtain a target urine pH of 6.3. Each experimental period was preceded by a 7d wash out period, in which the 0.06% Mg food was fed, followed by a 14d feeding period of the appropriate food. Two 24 h total urine collections were performed (d13: Acidified, d14: Un-acidified; immediately iced) and blood was collected on d14. Dry matter intake (p≥0.13) and BW (p≥0.13) were not affected by treatment. Plasma Mg concentration increased linearly with increasing dietary Mg (0.54, 0.56, 0.58 mM; p = 0.001). In contrast, plasma concentrations of threonine, histidine and tryptophan were lower in cats fed 0.12% Mg compare with 0.06 or 0.18% Mg (quadratic, p≤0.03). Urine output (p≥0.17), pH (p≥0.55), NH3 (p≥0.21) and titratable acidity of urine (p≥0.14) were similar across treatments. Urinary histamine excretion responded quadratically (p = 0.02) to treatment (3483, 3369, 3986 ng/d), whereas urinary histamine: Creatinine (p≥0.43) and plasma histamine concentration (p≥0.55) were unaffected. Differences were not detected among treatments in total histamine, cellular + noncellular histamine, (p≥0.11) or antigen-induced (p≥0.21) histamine release in whole blood. These data indicate that dietary Mg concentration, from 0.06-0.18%, does not affect urinary acidity or circulating histamine concentrations, however, supplying Mg at 0.18% may increase urinary histamine excretion.

SK&F 93574, a histamine H2-receptor antagonist, releases histamine in the dog

This study was designed to establish whether SK&F 93574 releases histamine in dogs. Three female beagle dogs each received single infusions (on separate days) of each of SK&F 93574 (2.5 mg kg-1), polyvinylpyrrolidone (PVP, 20 mg kg-1) and sterile saline. The treatments were given at 14 day intervals by rapid intravenous infusion at 0.5 mL kg-1 min-1 for 2 minutes. Dogs showed clinical signs of histamine release such as vasodilation, licking lips, head drooping and increased gut movement after treatment with the known histamine releaser PVP or the test compound SK&F 93574. These signs were of similar severity and duration for the two compounds. No such changes were observed when the dogs received vehicle alone. Treatment with PVP or SK&F 93574 also resulted in markedly elevated plasma histamine concentrations (greater than 10-fold increase over control). It is concluded that intravenous administration of SK&F 93574 to dogs is associated with histamine release.

Mesenteric lymph node transcriptome profiles in BALB/c mice sensitized to three common food allergens

BackgroundFood allergy is a serious health concern among infants and young children. Although immunological mechanism of food allergy is well documented, the molecular mechanism(s) involved in food allergen sensitization have not been well characterized. Therefore, the present study analyzed the mesenteric lymph node (MLN) transcriptome profiles of BALB/c mice in response to three common food allergens.ResultsMicroarray analysis identified a total of 1361, 533 and 488 differentially expressed genes in response to β-lactoglobulin (BLG) from cow's milk, ovalbumin (OVA) from hen's egg white and peanut agglutinin (PNA) sensitizations, respectively (p < 0.05). A total of 150 genes were commonly expressed in all antigen sensitized groups. The expression of seven representative genes from microarray experiment was validated by real-time RT-PCR. All allergens induced significant ear swelling and serum IgG1 concentrations, whereas IgE concentrations were increased in BLG- and PNA-treated mice (p < 0.05). Treatment with OVA and PNA significantly induced plasma histamine concentrations (p < 0.05). The PCA demonstrated the presence of allergen-specific IgE in the serum of previously sensitized and challenged mice.ConclusionsImmunological profiles indicate that the allergen dosages used are sufficient to sensitize the BALB/c mice and to conduct transcriptome profiling. Microarray studies identified several differentially expressed genes in the sensitization phase of the food allergy. These findings will help to better understand the underlying molecular mechanism(s) of food allergen sensitizations and may be useful in identifying the potential biomarkers of food allergy.

Pre- and post-operative plasma histamine concentrations in 35 dogs with mast cell tumours

This study aims to determine if plasma histamine concentrations (PHCs) reduced following mast cell tumour (MCT) removal and to further confirm that dogs with MCTs have higher PHCs compared to healthy dogs. Blood samples were taken pre-operatively and 2 to 4 h post-operatively in 35 dogs with cytologically confirmed MCTs undergoing removal and ten control dogs undergoing ovariohysterectomy. An enzyme immunoassay was used to determine the PHC. There was no statistically significant difference in the change in PHCs in dogs with MCTs compared to the control dogs undergoing ovariohysterectomy. It was confirmed that dogs with MCTs have higher PHCs compared to normal dogs. This study showed that dogs with MCTs had statistically significant hyperhistaminemia compared with the control dogs. This could lead to gastroduodenal ulceration which may be subclinical or cause clinical signs such as vomiting, diarrhea, or anemia and supports the use of H2 receptor antagonist drugs pre-operatively. Despite the rapid metabolism of histamine, abdominal surgery causes ongoing and sustained histamine release which increased plasma concentrations. Blood sampling at a later stage post-operatively may have yielded different results.

The Role of Mast Cells in Citric Acid-Induced Airway Constriction and Cough

Inhalation of citric acid (CA) causes airway constriction and coughing. To investigate the role of mast cells in CA-induced airway constriction and cough, three experiments using guinea pigs were carried out. In the first experiment, we used compound 48/80 to deplete mast cells, cromolyn sodium to stabilize mast cells, MK-886 to inhibit synthesis of leukotrienes, pyrilamine to antagonize histamine H1 receptor, methysergide to antagonize serotonin receptor, and indomethacin to inhibit cyclooxygenase. In the second experiment, compound 48/80-pretreated animals were divided into 2 parts; the first one was used to test the role of exogenous leukotriene (LT) C4, while the second one to test the role of exogenous histamine. Decreases in respiratory compliance (Crs) and forced expiratory volume in 0.1 sec (FEV0.1) were used as indicators for airway constriction in anesthetized guinea pigs. CA-induced cough was recorded for 12 min using a barometric body plethysmograph in conscious animals. In the third experiment, the activation of mast cells upon CA inhalation was investigated by determining lung tissue or arterial plasma histamine concentration in animals. Exposure to CA induced marked airway constriction and increase in cough number. Compound 48/80, cromolyn sodium, MK-886 and pyrilamine, but not indomethacin or methysergide, significantly attenuated CA-induced airway constriction and cough. Injection of LTC4 or histamine caused a significant increase in CA-induced airway constriction and cough in compound 48/80-pretreated animals. In addition, CA inhalation caused significant increase in lung tissue and plasma histamine concentrations, which were blocked by compound 48/80 pretreatment. These results suggest that mast cells play an important role in CA aerosol inhalation-induced airway constriction and cough via perhaps mediators including LTs and histamine.

Metabolism of histamine in tissues of primary ductal breast cancer

Histamine performs an important role in the pathologic and physiologic aspects of the breast gland. Among monoamines, histamine demonstrates the greatest proliferative activity in breast cancer. The aim of the study was to evaluate histamine concentration in plasma and tissues of breast cancer dependent on the activity of histamine metabolism enzymes in neoplasmatic tissues of the breast gland. Ninety-five women aged 38 to 70 years were divided into 2 groups. The control group (group I) consisted of 30 healthy women. Group II consisted of 65 women with primary ductal breast cancer. The concentration of histamine in plasma was assessed by immunoenzymatic method. The concentration of histamine in cancerous tissues of the breast and the metabolism of histamine enzymes, specially histidine decarboxylase, decarboxylase of aromatic l-amino acids, N-histamine methyltransferase, monoamine oxydase B, and diamine oxydase, were determined using isotope technique. In the course of 24 hours, excretion of N-methylimidazoleacetic acid was evaluated by the methods of chromatography. The statistical analysis was made based on Statistica Pl Ed (StatSoft, Cracow, Poland, 1998). A significant increase in the concentration of histamine in plasma ( P < .01) and tissues of ductal breast cancers ( P < .001), and in the activity of histidine decarboxylase ( P < .01), aromatic l-amino acids ( P < .05), and histamine methyltransferase ( P < .05) was found. Activity of monoamine oxidase B ( P < .01) and diamine oxidase ( P < 0.01) and excretion of N-methylimidazoleacetic acid were significantly decreased compared with the control group ( P < 0.001). The conclusions are as follows: (1) Concentration of histamine in the plasma of women is dependent on the concentration of histamine in the tissues of ductal breast cancers. (2) The significant increase of histamine in cancerous tissues of ductal breast cancer could suggest the participation of this monoamine in the development of breast cancer. (3) The increase of histamine concentrations in ductal breast cancer tissues can be connected with the disturbances of the balance between synthesis and enzymatic inactivation of this monoamine. (4) The concentration of histamine in the plasma of women with ductal breast cancers is dependent on the number of involved lymph nodes and the grade of histologic malignancy.

Effect of Protein Depletion on Host and Tumor Response to Paclitaxel in Experimental Animals

Abstract: The present study is aimed to examine the possible effects of Protein Malnutrition (PM) on the therapeutic activity and toxicity of paclitaxel in mice implanted with Ehrlich carcinoma cells. Mice that were fed either with standard or low protein diets were treated with a single dose of paclitaxel (10 mg kg-1, i.p.). Paclitaxel administration increased the tumor growth delay of Ehrlich carcinoma from 2.8 days in protein deficient animals to 4.9 days in normal feeding mice and this represented about 43% increase in tumor growth delay. Furthermore, protein deficiency also interfered with the antitumor activity of paclitaxel. The percent survival of tumor-bearing mice after paclitaxel treatment were 56 and 19% in normal fed and protein deficient animals, respectively. Moreover, Paclitaxel administration increased the serum level of creatine phosphokinase isoenzyme (CPK-MB) in both groups, with maximum effect appeared after 48 h. Seventy two hours later, the levels was reduced to the normal values in normal fed animals while in protein malnourished mice, the activity was found to be high. In addition, paclitaxel administration significantly increased the plasma histamine concentration after 10 min and persisted for 120 min in animals on protein malnourished diet, however, in animals on a normal fed diet, histamine concentration reached the normal level after 120 min of paclitaxel administration. In conclusion, Paclitaxel administration exerts its toxic effects on both protein malnourished and normal feeding animals, however, its toxicity is enhanced and therapeutic activity is reduced in the protein deficient animals.

High dose of lipopolysaccharide pre-treatment prevents OVA-induced anaphylactic decreases in rectal temperature in the immunized mice

It remains unclear whether lipopolysaccharide (LPS) pre-treatment, which prevents Th2-type responses via Toll-like receptor 4 (TLR4), inhibits anaphylaxis. To determine the dose-dependent effects of LPS pre-treatment on anaphylactic decreases in rectal temperature caused by ovalbumin (OVA) re-exposure in immunized mice, C3H/HeN mice were divided into vehicle/OVA (0mg/kg LPS), L-LPS/OVA (0.5mg/kg LPS), M-LPS/OVA (1.0mg/kg LPS) and H-LPS/OVA (3.0mg/kg LPS) groups. After receiving these treatments, the mice were systemically immunized with OVA. Negative control mice were not immunized with OVA (N-OVA). After measuring the serum levels of OVA-specific IgE and IgG1 antibodies, the mice were examined for changes in their rectal temperature and plasma histamine concentration after OVA re-exposure. The allergen-specific IgE and IgG1 concentrations in sera from L-LPS/OVA, M-LPS/OVA and H-LPS/OVA mice were significantly lower than those in sera from vehicle/OVA mice despite OVA immunization. However, the antibody levels in all OVA-immunized mice, with the exception of the IgG1 levels in H-LPS/OVA mice, were significantly higher than those in N-OVA mice. Interestingly, H-LPS/OVA mice were the only group that did not exhibit a decrease in rectal temperature, since the rectal temperatures in vehicle/OVA, L-LPS/OVA and M-LPS/OVA mice were significantly decreased by OVA re-exposure. Furthermore, the decrease in rectal temperature after OVA re-exposure in L-LPS/OVA mice, which did not exhibit an increase in the plasma histamine concentration, was significantly prevented by treatment with a platelet-activating factor (PAF) receptor antagonist alone. Taken together, the present results indicate that high-dose LPS pre-treatment may prevent anaphylaxis in OVA-immunized mice, and that this mechanism may depend on inhibition of the IgG-PAF pathway rather than the IgE-histamine pathway.

Comparison of plasma histamine levels after intravenous administration of hydromorphone and morphine in dogs

This study compared plasma histamine concentrations, behavioral and cardiovascular parameters following intravenous administration of hydromorphone and morphine in conscious dogs. Five adult female dogs received a 15-sec bolus injection of saline, hydromorphone (0.1 and 0.2 mg/kg) or morphine (0.5 and 1.0 mg/kg) randomly at weekly intervals. Blood samples were collected from the jugular vein before and at 1, 2, 5, 15, 30, 60 and 120 min after drug administration. Plasma histamine concentration, noninvasive oscillometric blood pressure, heart rate and rhythm were evaluated. Data were analyzed with repeated measures anova and Tukey-Kramer post hoc test with a 5% significance level. Median plasma histamine increased significantly only after the higher dose of morphine. Maximum plasma histamine measured was 0.8 ng/mL after saline and, after the lower and higher doses, respectively, 10.2 and 9.7 ng/mL for hydromorphone, and 440 and 589 ng/mL for morphine. One dog became hypotensive immediately after receiving the highest dose of morphine. Occasional ventricular premature contractions occurred in one dog after both opioids and dosages. No dogs vomited or defecated, but all salivated profusely with both opioids. Neuroexcitation occurred in four dogs following each opioid. In conclusion, intravenous hydromorphone induced minimal histamine release and was well tolerated by these conscious healthy dogs.

The Effect of Fexofenadine on Pruritus in a Mouse Model (HR-ADf) of Atopic Dermatitis

Fexofenadine, a histamine H1-receptor antagonist, is approved for the treatment of pruritus associated with atopic dermatitis. The effects of fexofenadine on scratching behaviour, and plasma levels of histamine and eotaxin were assessed in a new model of atopic dermatitis. Mice fed a diet low in Mg2+ and Zn2+ (special diet S) were compared with mice on a normal diet (N) or diet S plus fexofenadine HCl for weeks 0-10 (S + F(0-10)), 0-5 (S + F(0-5)) or 6 - 10 (S + F(6-10)) (seven mice per group). Compared with group N, group S mice showed significantly greater scratching frequency, and plasma histamine and eotaxin concentrations; these three variables were significantly lower in group S + F(0-10) than in group S. Scratching frequency increased when fexofenadine was discontinued. Fexofenadine significantly reduced mast cell and eosinophil numbers. Histamine may be important in the pathological changes seen in this model of atopic dermatitis, suggesting that it might aid future development of antihistamines for the treatment of atopic dermatitis.

Plasma histamine concentration and histamine detection in peripheral blood eosinophils in cats

Plasma histamine levels were measured in 11 clinically healthy cats and 15 cats with allergic dermatitis. Histamine levels were markedly elevated in 5/15 allergic cats. A calcium ionophore, A23187, stimulates histamine release from feline peripheral blood cells. Immunostaining of blood smears from clinically healthy cats revealed that approximately 10% of eosinophils possessed histamine-containing granules. These results indicate that some peripheral eosinophils in cats contain histamine and can release histamine by appropriate stimulation.

Prophylactic effect of pemirolast, an antiallergic agent, against hypersensitivity reactions to paclitaxel in patients with ovarian cancer

We have previously shown that sensory nerve peptides contribute to the pathogenesis of pulmonary hypersensitivity reactions (HSRs) to paclitaxel in rats. Moreover, pemirolast, an antiallergic agent, reverses the HSRs to paclitaxel, although the mechanism is considered to result from the blockade of paclitaxel-induced release of sensory peptides, rather than the inhibition of histamine release. In the present study, we investigated the preventive effect of pemirolast against acute HSRs in a total of 84 patients who undertook postoperative paclitaxel plus carboplatin chemotherapy every 4 weeks for ovarian cancer. Patients were assigned to receive oral lactose (placebo) or pemirolast (10 mg), 2 hr before paclitaxel infusion. All patients received conventional premedication, including oral diphenhydramine, intravenous ranitidine and intravenous dexamethasone, 30 min before paclitaxel infusion. The HSRs that led to the discontinuance of paclitaxel infusion (grade>or=2) occurred in 5 of 42 patients in placebo group, whereas none of pemirolast-treated 42 patients showed any signs of HSRs. Plasma histamine concentrations were not changed after paclitaxel infusion in either group. Our present findings suggest that pemirolast is potentially useful for prophylaxis of paclitaxel-induced HSRs. In this respect, the use of pemirolast as premedication is expected to be beneficial to the safety management in patients who undergo chemotherapy containing paclitaxel.

Evaluation of histamine release during constant rate infusion of morphine in dogs

ObjectiveTo evaluate histamine release and selected physiologic variables during constant rate infusion (CRI) of morphine in dogs. AnimalsFive healthy, conscious, intact female dogs. Material and methodsUsing a Latin square, repeated-measures design, dogs were randomly assigned to three treatment groups to receive a 4-hour CRI of saline (SAL), or a loading dose of morphine at 0.3 mg kg−1 (LM), or 0.6 mg kg−1 (HM), followed by an infusion of 0.17 mg kg−1 hour−1 (LM) and 0.34 mg kg−1 hour−1 (HM) respectively. Dogs received each of the three treatments at intervals of at least 7 days. Plasma histamine concentration, skin flushing, edema and wheals, heart rate and rhythm and non-invasive arterial blood pressure were measured before the loading dose and at 1, 2, 5, 15, 30, 60, 120, 180 and 240 minutes during the CRI, or at the time of occurrence. ResultsThe loading dose induced the highest histamine release in the HM group being statistically higher than the SAL group. The histamine release obtained in the LM group after the loading dose did not differ from SAL. During the infusion, plasma histamine levels were numerically higher in the LM group. Besides one dog that developed hypotension for 2 minutes after the loading dose in the HM group and one dog that showed occasional ventricular premature contractions during both morphine infusions, cardiovascular variables were similar among the three treatment groups. Conclusions and Clinical relevanceBoth doses of morphine induced variable histamine release with minimal adverse cardiovascular effects in these concious, healthy dogs. The plasma histamine levels obtained may be associated with significant hemodynamic changes in patients with limited cardiovascular reserve and sympathetic nervous tone.

Histamine release during adult cardiopulmonary bypass

Histamine, an inflammatory mediator in its own right, may also be a marker for a more widespread systemic inflammatory process. In this study we have examined variations in plasma histamine concentrations produced during the course of cardiac surgery involving cardiopulmonary bypass, the relationship between these variations and intra-operative events. By assays of serum tryptase and CD-63 expression we have also attempted to identify the source of histamine. Histamine concentrations that were significantly raised from baseline level were demonstrated. These were elevated from the time of aortic cross-clamping and continued to be raised for 24 h postoperatively (p < 0.00625). This was associated with an increase in CD-63 expression (p < 0.025) (but not an increase in tryptase concentration) following aortic cross-clamping and protamine administration, suggesting that basophils are the source of histamine. 41% of patients had arrhythmias in the post bypass period. The rise in histamine levels was not related to the incidence of cardiac arrhythmias.

Plasma Histamine And Serotonin Levels In Children With Nephrotic Syndrome And Acute Poststreptococcal Glomerulonephritis

Plasma histamine and serotonin concentrations were measured using fluorimeteric assay in 40 children with renal diseases. Minimal change nephrotic syndrome (15) focal segmental glomerulosclerosis(10) and acute poststreptococcal glomerulonephritis(15) to determine the relation between plasma levels of histamine and serotonin and these various types of renal diseases in children. Plasma histamine level was significantly increased in group of children with acute poststreptococcal glomerulonephritis. Plasma serotonin levels were significantly increased in all 3 groups of patient, when compared with those of controls. Raised plasma histamine in acute poststreptococcal glomerulonephritis group may be evidence of the acute immunological inflammation and defective renal excretion due to mild renal impairment in these children. Raised plasma serotonin in all 3 groups of patients may be due to diminished uptake and release of serotonin from platelets in children with minimal change nephrotic syndrome and focal segmental glomerulosclerosis and due to defective renal execretion in children with acute poststreptococcal glomerulo-nephritis.

Plasma Histamine And Serotonin Levels In Children With Nephrotic Syndrome And Acute Poststreptococcal Glomerulonephritis

Plasma histamine and serotonin concentrations were measured using fluorimeteric assay in 40 children with renal diseases. Minimal change nephrotic syndrome (15) focal segmental glomerulosclerosis(10) and acute poststreptococcal glomerulonephritis(15) to determine the relation between plasma levels of histamine and serotonin and these various types of renal diseases in children. Plasma histamine level was significantly increased in group of children with acute poststreptococcal glomerulonephritis. Plasma serotonin levels were significantly increased in all 3 groups of patient, when compared with those of controls. Raised plasma histamine in acute poststreptococcal glomerulonephritis group may be evidence of the acute immunological inflammation and defective renal excretion due to mild renal impairment in these children. Raised plasma serotonin in all 3 groups of patients may be due to diminished uptake and release of serotonin from platelets in children with minimal change nephrotic syndrome and focal segmental glomerulosclerosis and due to defective renal execretion in children with acute poststreptococcal glomerulo-nephritis.

Evaluation of histamine release during constant rate infusion of morphine in dogs

Previous studies have reported increased plasma histamine levels after single intravenous injections of morphine in dogs. The goals of this study were to evaluate histamine release and selected physiologic parameters during constant rate infusion (CRI) of morphine in dogs. Five adult healthy, conscious, intact female dogs were studied. Using a Latin square, repeated-measures design, dogs were randomly assigned to three treatment groups to receive either a loading dose of morphine at 0.3 mg kg−1 IV followed by a CRI of 0.17 mg kg−1 hour−1 IV (LM) or 0.6 mg kg−1 IV followed by a CRI of 0.34 mg kg−1 hour−1 IV (HM) or a bolus and a CRI of saline (SAL). Dogs received each of the three treatments at intervals of at least 7 days. Plasma histamine concentrations, skin flushing, edema and wheals, heart rate and rhythm and noninvasive arterial blood pressure were measured before and at 1, 2, 5, 15, 30, 60, 120, 180 and 240 minutes during the CRI or at the time of occurrence. Observer was blinded to the treatment given. Results showed that the highest histamine release occurred in the HM group at 1 minute after the loading dose (median 10.6 ng mL−1), which was significantly different from the LM (median 1.85 ng mL−1) and the SAL (median 0.26 ng mL−1) groups. By comparison, no other significant differences in plasma histamine were seen for the remaining time points, although during the CRI, plasma histamine levels were numerically highest in the LM group. One dog that developed hypotension for two minutes after the loading dose in the HM group and one dog showed occasional ventricular premature contractions during both morphine CRIs, otherwise cardiovascular parameters were similar among the three treatment groups. In conclusion, both doses of morphine induced variable histamine release with minimal cardiovascular adverse effects in these awake, healthy dogs. The plasma histamine levels obtained may be associated with significant hemodynamic changes in patients with limited cardiovascular reserve and reduced sympathetic tone.

Effect of H1- and H2-receptor antagonists on the hemodynamic changes induced by the intravenous administration of ketamine in sevoflurane-anesthetized cats

The anesthetic ketamine has been reported to cause both an increase of the plasma histamine concentration, notably in cats, and a cardiovascular depression. The latter has been described in humans and in other species. However the relevance of the histamine fluctuation for the ketamine-induced hemodynamic changes has not been determined. We studied the contribution of histamine to the hemodynamic effects induced by IV ketamine (7 mg/kg) in 12 sevoflurane anesthetized cats, of which half had been pre-treated with combined H(1)- and H(2) -receptor antagonists. The mean arterial pressure (MAP) and the heart rate (HR) from both untreated (group C) and pre-treated (group AH) cats were recorded before and after the ketamine administration. The plasma histamine concentration was also measured. Plasma histamine fluctuations in the control and the antihistamine-treated group followed a similar pattern (no statistical differences); an initial rise that peaked 2 min after ketamine injection (from 0.63 +/- 0.11 ng/ml to 2.22 +/- 0.69 ng/ml in the C group, and from 0.71 +/- 0.10 ng/ml to 1.09 +/- 0.28 ng/ml in the AH group) followed by an immediate decrease in plasma concentrations. As for the hemodynamic variables under analysis, in the control group ketamine administration was followed by an early 30.3 +/- 8.1% reduction (p < 0.005) in the MAP with no associated changes in the HR. In the antihistamine pre-treated group, ketamine caused a further decrease of the MAP (41.7 +/- 2.3%), and a significant (p < 0.01) 11.6 +/- 2.9% reduction of the HR. Ketamine in anesthetized cats triggers histamine release and induces cardiovascular depression. The depression is more pronounced under the blockade of histamine activity through histamine receptor antagonists.

Effect of moderate stress on plasma histamine concentration in laboratory dogs

Effect of moderate stress on plasma histamine concentration in laboratory dogs

Influence of different training and outdoor conditions on plasma histamine and cortisol concentrations in search-and-rescue dogs

Influence of different training and outdoor conditions on plasma histamine and cortisol concentrations in search-and-rescue dogs