Combined treatment with H1 and H4 receptor antagonists reduces inflammation in a mouse model of atopic dermatitis.

BACKGROUND: Histamine 4 receptor (H4R) antagonists are considered as new therapeutics for the treatment of atopic dermatitis (AD) and first clinical trials have already shown promising results. Histamine 1 receptor (H1R) antagonists are traditionally used to treat AD although the evidence for the efficacy is weak. The combined blockade of both, H1R and H4R, might provide synergistic anti-inflammatory. OBJECTIVE: The study was performed to test the anti-inflammatory potential of a combined treatment with an H1R and an H4R antagonist in a mouse AD model. METHODS: The development of ovalbumin-induced AD-like skin lesions was analysed mice treated with the H1R inverse agonist mepyramine, the H4R antagonist JNJ-39758979 or a combination of both. RESULTS: Mice treated with mepyramine plus JNJ-39758979 showed less severe skin lesions, with a diminished influx of inflammatory cells, a reduced epidermal thickening and a lower level of IL-33 in lesional skin. Scratching behaviour was ameliorated in mice treated with the combination. Moreover, total numbers of skin-draining lymph node cells and splenocytes were significantly reduced. Both substances given alone did not elicit this strong anti-inflammatory effect. CONCLUSION: H1R and H4R antagonists provide synergistic anti-inflammatory effects in a mouse model of AD. The combined therapy with H1R and H4R antagonists might represent a new strategy for the treatment of AD.

Synergistic interaction between diclofenac and pyrilamine on nociception, inflammation, and gastric damage in rats.

Experiments using nonsteroidal anti-inflammatory drugs (NSAIDs) alone have produced limited antinociceptive effects in animal models. For this reason, the number of studies involving the administration of NSAIDs along with an adjuvant drug harboring different mechanisms of action has increased enormously. Here, combinations of diclofenac and pyrilamine were used to determine their influence on nociception (formalin test), inflammation (paw inflammation produced by carrageenan), and gastric damage in rodents. Diclofenac, pyrilamine, or combinations of diclofenac and pyrilamine produced antinociceptive and anti-inflammatory effects in the rat. The systemic administration of diclofenac alone and in combination with pyrilamine produced significant gastric damage. Effective dose (ED) values were determined for each individual drug, and isobolograms were prepared. The theoretical ED values for the antinociceptive (systemic, 35.4 mg/kg; local, 343.4 µg/paw) and the anti-inflammatory (37.9 mg/kg) effects differed significantly from the experimental ED values (systemic antinociception, 18.1 mg/kg; local antinociception, 183.3 µg/paw; anti-inflammation, 10.6 mg/kg). Therefore, it was concluded that the interactions between diclofenac and pyrilamine are synergistic. The data suggest that the diclofenac-pyrilamine combinations can interact at the systemic and local peripheral levels, thereby offering a therapeutic alternative for the clinical management of inflammatory pain.

Protective effects of histamine on Gq-mediated relaxation in regenerated endothelium.

In the porcine coronary artery, regenerated endothelium is dysfunctional as regards the responses to endothelium-dependent agonists. The current study aimed to determine the possible involvement of histamine in such dysfunction. Pigs were treated chronically with pyrilamine (H1 receptor inhibitor, 2 mg·kg(-1)·day(-1)) with part of their coronary endothelium and allowed to regenerate for 28 days after balloon denudation. The results showed a reduction in relaxation to bradykinin (Gq protein dependent) only in the pyrilamine-treated group (area under the curve, 269.7 ± 13.4 vs. 142.0 ± 31.0, native endothelium vs. regenerated endothelium) but not in the control group (253.0 ± 22.1 vs. 231.9 ± 29.5, native endothelium vs. regenerated endothelium). The differences in the relaxation to serotonin (Gi protein dependent) between native and regenerated endothelium were not affected by the pyrilamine treatment (control group, 106.3 ± 17.0 vs. 55.61 ± 12.7; and pyrilamine group, 106.0 ± 8.20 vs. 49.30 ± 6.31, native endothelium vs. regenerated endothelium). These findings indicate that during regeneration of the endothelium, the activation of H1 receptors by endogenous histamine may be required to maintain the endothelium-dependent Gq protein-mediated relaxation to bradykinin, suggesting a beneficial role of the monoamine in the process of endothelial regeneration.

Mast cell mediators cause early allergic bronchoconstriction in guinea-pigs in vivo: a model of relevance to asthma.

One feature of allergic asthma, the EAR (early allergic reaction), is not present in the commonly used mouse models. We therefore investigated the mediators involved in EAR in a guinea-pig in vivo model of allergic airway inflammation. Animals were sensitized using a single OVA (ovalbumin)/alum injection and challenged with aerosolized OVA on day 14. On day 15, airway resistance was assessed after challenge with OVA or MCh (methacholine) using the forced oscillation technique, and lung tissue was prepared for histology. The contribution of mast cell mediators was investigated using inhibitors of the main mast cell mediators [histamine (pyrilamine) and CysLTs (cysteinyl-leukotrienes) (montelukast) and prostanoids (indomethacin)]. OVA-sensitized and challenged animals demonstrated AHR (airway hyper-responsiveness) to MCh, and lung tissue eosinophilic inflammation. Antigen challenge induced a strong EAR in the sensitized animals. Treatment with a single compound, or indomethacin together with pyrilamine or montelukast, did not reduce the antigen-induced airway resistance. In contrast, dual treatment with pyrilamine together with montelukast, or triple inhibitor treatment, attenuated approximately 70% of the EAR. We conclude that, as in humans, the guinea-pig allergic inflammation model exhibits both EAR and AHR, supporting its suitability for in vivo identification of mast cell mediators that contribute to the development of asthma. Moreover, the known mast cell mediators histamine and leukotrienes were major contributors of the EAR. The data also lend further support to the concept that combination therapy with selective inhibitors of key mediators could improve asthma management.

Opposite effects of mepyramine on JNJ 7777120-induced amelioration of experimentally induced asthma in mice in sensitization and provocation.

BACKGROUND: Histamine is detected in high concentrations in the airways during an allergic asthma response. In a murine model of allergic asthma, JNJ 7777120, an antagonist at the histamine H(4) receptor, reduces asthmatic symptoms, while the histamine H(1) receptor-selective antagonist mepyramine is virtually without effect. In the present study, we analyzed the effect of combined antagonism at the histamine H(1) and H(4) receptors in a murine asthma model in relation to the timing of their application, i.e. sensitization or provocation. METHODOLOGY/PRINCIPAL FINDINGS: Asthma was induced in mice by sensitization and provocation with ovalbumin. JNJ 7777120 and/or mepyramine were injected subcutaneously either during sensitization or during provocation, and typical asthma parameters were analyzed. JNJ 7777120, but not mepyramine, reduced serum concentrations of anti-OVA IgE, inflammatory infiltrations in lung tissue, and eosinophilia in bronchoalveolar-lavage (BAL)-fluids independently of the timing of application. Upon application of JNJ 7777120 plus mepyramine in combination during provocation, mepyramine inhibited the effects of JNJ 7777120. In contrast, when applied during sensitization, mepyramine enhanced the disease-ameliorating effects of JNJ 7777120. CONCLUSIONS/SIGNIFICANCE: Our study indicates that both histamine H(1) and H(4) receptors play important roles in the course of murine experimental asthma. Unexpectedly, the contribution of these receptors to the pathogenesis differs between the two phases, sensitization or provocation. Since in human asthma, repeated contact to the allergen is not only provocation but also a boost of sensitization, a combined pharmacological targeting of histamine H(1) and H(4) receptors could be taken into consideration as an option for the prevention of asthma and maybe other allergic diseases.

Strain-dependent effects of the histamine H4 receptor antagonist JNJ7777120 in a murine model of acute skin inflammation.

The effects of the histamine H(4) receptor antagonist JNJ7777120 were evaluated in a model of acute skin inflammation induced by local application of croton oil. The influence of strain on the effect of JNJ7777120 was investigated in four different mouse strains (CD-1, NMRI, BALB/c and C57BL/6J). In CD-1 mice, JNJ777720 (30-100 mg/kg subcutaneously, s.c.) exerted a dose-dependent inhibition of croton oil-induced ear inflammation and polymorphonuclear leucocyte infiltration, as confirmed by histological evaluation of ear tissues. JNJ7777120 (30-100 mg/kg) did not reduce ear oedema in NMRI, BALB/c or C57BL/6J mice. The positive control, dexamethasone (2 mg/kg s.c.) induced significant anti-inflammatory effects only in CD-1 and NMRI mice. In these strains, also the histamine H(1) -receptor blocker pyrilamine (30 mg/kg s.c.) significantly reduced ear oedema at 2 h after croton oil challenge, being as effective as JNJ7777120 in CD-1 mice. Taken together, these data demonstrate that the H(4) receptor antagonist JNJ7777120 may reduce acute croton oil-induced skin inflammation as effectively as H(1) receptor blockade. However, present experiments evidenced for the first time marked strain-related differences in the JNJ7777120 pharmacological activity, which have to be carefully considered when using this ligand to characterize histamine H(4) receptor functions in murine models and translating preclinical data to clinical human settings.

[Roles of histamine in the exacerbated allergic dermatitis].

We established a novel dermatitis model in mice earlobes and analyzed the roles of histamine using specific antagonists for histamine receptors. After sensitization with picryl chloride (PiCl) by painting it on the earlobes of cyclophosphamide-treated mice, 12-O-tetradecanoylphorbol 13-acetate (TPA) was painted twice at the same site, and then allergic inflammation was induced by painting with PiCl. Histamine antagonists and cyclosporin A were administered i.v. The application of TPA shifted the PiCl-induced allergic inflammation from a delayed-type response to a biphasic response and increased the infiltration of eosinophils and mast cells at the inflammatory site. In this model, the PiCl-induced increase in the thickness of the earlobe in the immediate phase was suppressed by the histamine H1 antagonist pyrilamine. In contrast, the increase in the swelling in the late phase and the infiltration of eosinophils were suppressed by the H3/H4 antagonist thioperamide. The inhibitory effect of the combined treatment with pyrilamine and thioperamide on TPA-modified contact dermatitis was as potent as that of cyclosporin A. Histamine plays significant roles in early-phase swelling via H1 receptors and in late-phase swelling via H3/H4 receptors in this TPA-modified allergic dermatitis model.

Histamine H(1) antagonist treatment with pyrilamine reduces nicotine self-administration in rats.

Nicotine has been definitively shown to be critically involved in the neural bases of tobacco addiction. However, nicotine releases a wide variety of neurotransmitters. Nicotine-induced dopamine release has been shown to play a key role in facilitating nicotine self-administration. Other transmitter systems may also play important roles in the pharmacological effects of nicotine and may provide important leads for combating nicotine self-administration. Clozapine, an antipsychotic drug, which blocks a variety of different transmitter receptors including serotonin 5HT(2) and histamine H(1) receptors, has been found to decrease smoking. Previously we found that the serotonin 5HT(2) antagonist, ketanserin, significantly reduced nicotine self-administration. In the current study, we assessed histamine H(1) receptor interaction with nicotine self-administration. Young adult female Sprague-Dawley rats were fitted with IV catheters and trained to self-administer nicotine (0.03mg/kg/infusion). Acute doses of 40mg/kg of pyrilamine, a histamine H(1) antagonist, significantly reduced nicotine self-administration. We also found that repeated injections (20mg/kg) or chronic infusion via osmotic minipumps (50mg/kg/day) of pyrilamine also significantly decreased nicotine self-administration. The peripherally restricted H(1) antagonist ebastine was ineffective in reducing nicotine self-administration, pointing to central H(1) receptor blockade as key for the effectiveness of pyrilamine. H(1) antagonists may be a promising avenue to explore for new treatments to aid smoking cessation.

Efficacy of mepyramine maleate treatment in dogs with angioedema.

Twenty-seven dogs with angioedema, were enrolled in this clinical study. The cases were randomly assigned to the treatment group (n=15) and untreated placebo control group (n=12). It was concluded that mepyramine maleate has the potential to be helpful for dogs with angioedema.

Primary dysmenorrhea among Mexican university students: prevalence, impact and treatment.

OBJECTIVE: To evaluate the prevalence, impact and treatment of primary dysmenorrhea among Mexican university students. STUDY DESIGN: A multiple-choice questionnaire was administered to 1539 students in six university programs: medicine, nursing, nutrition, dentistry, pharmacy and psychology. Data on the presence, severity, symptoms, treatment and limitations caused by dysmenorrhea were obtained and analyzed. RESULTS: The mean+/-SD age of the women was 20.4+/-2.0 years; the mean age of menarche was 12.3+/-1.5 years. A total of 64% of the women experienced dysmenorrhea. Dysmenorrhea was more prevalent among nutrition and psychology students than among medicine, pharmacy and dentistry students (p<0.05). Dysmenorrhea was mild in 36.1% of women, moderate in 43.8% and severe in 20.1%. Nursing students showed an intensity of pain that was significantly higher than that of medicine and dentistry students (p<0.05). Sixty-five percent of the women with dysmenorrhea reported that it limited their daily activities, and 42.1% reported school absenteeism (SA) as a result. Of those who experienced dysmenorrhea, 25.9% consulted a physician, and 61.7% practiced self-medication (SM). The most common medications used were an over-the-counter (OTC) medication with paracetamol (an analgesic), pamabrom (a diuretic), and pyrilamine (a histamine antagonist), another OTC with metamizol (a non-steroidal anti-inflammatory drug [NSAID]) plus butylhioscine (an antispasmodic drug) and naproxen (a NSAID). Of those women using prescribed medications, 18.4% reported complete remission of their symptoms, while 78.1% reported little to moderate alleviation, and 3.6% reported no effect on their menstrual distress. Similarly, of the women who practiced SM, 23.4% reported complete relief, 75.5% reported little to moderate effectiveness, and 1.0% reported no efficacy. CONCLUSION: The prevalence of dysmenorrhea among Mexican university students is high, and the pain that these women suffer can be severe, disabling and result in short-term SA. The pain is often not completely relieved despite the use of medication. It is necessary to improve the therapeutic options for relief of pain caused by dysmenorrhea and to minimize the impact of dysmenorrhea on social, economic and school activities.

Modification of the picryl chloride-induced allergic dermatitis model in mouse ear lobes by 12-O-tetradecanoylphorbol 13-acetate, and analysis of the role of histamine in the modified model.

BACKGROUND: In atopic dermatitis, inflammation induced by antigen-nonspecific stimuli further enhances the allergic inflammation. However, there is no experimental model in which allergic dermatitis is evoked where the inflammation has been induced by antigen-nonspecific stimuli. Here, we established a novel dermatitis model in mice and analyzed the role of histamine. METHODS: After sensitization with picryl chloride (PiCl) by painting on ear lobes of cyclophosphamide-treated mice, 12-O-tetradecanoylphorbol 13-acetate (TPA) was painted twice at the same site, and then allergic inflammation was induced by painting PiCl. Histamine antagonists and cyclosporine A (CsA) were administered intravenously. RESULTS: The application of TPA shifted the PiCl-induced allergic inflammation from a delayed-type response to a biphasic response, increased the infiltration of eosinophils and mast cells at the inflammatory site, shifted the cytokine milieu from Th1 to Th2 and induced the expression of thymic stromal lymphopoietin in the ear lobes. The PiCl-induced increase in the thickness of the ear lobe in the immediate phase was suppressed by the H1 antagonist pyrilamine. In contrast, the increase in the swelling in the late phase and the infiltration of eosinophils were suppressed by the H3/H4 antagonist thioperamide. The inhibitory effect of the combined treatment with pyrilamine and thioperamide on the TPA-modified contact dermatitis was as potent as that of CsA. CONCLUSION: Induction of the antigen-nonspecific inflammation by TPA enhanced the PiCl-induced allergic inflammation. Histamine plays significant roles in the early-phase swelling via H1 receptors, and the late-phase swelling via H3/H4 receptors in this TPA-modified allergic dermatitis model.

Differential responses to various classes of drugs in a model of allergic rhinitis in guinea pigs.

Different drugs from various pharmacological classes were compared for their ability to protect against the nasal effects of acute allergen challenge in a guinea pig model. In the model, sneezing and nose rubbing were recorded after an initial allergen challenge in guinea pigs previously sensitized to egg albumin. Four days later the same guinea pigs were re-challenged a second time when anesthetised. In these anaesthetized animals, nasal airway pressure, pulmonary inflation pressure and cellular infiltration into nasal lavage fluid were measured. The drug tested were autacoid antagonists (mepyramine--3mg/kg, cetirizine--3mg/kg and montelukast--10mg/kg), L-NAME (10 or 20mg/kg), heparin (20mg/kg) and dexamethasone (20mg/kg) given either intraperitoneally or intravenously; all were given shortly before challenge. Sneezing induced by allergen challenge was statistically significantly reduced by mepyramine, cetirizine and dexamethasone whereas only cetirizine reduced nose rubbing. Changes in nasal airway pressure due to allergen exposure were reduced by cetirizine, montelukast, L-NAME, and heparin, but not by mepyramine, nor dexamethasone. In the presence of L-NAME, nasal airway pressure actually changed in the opposite direction. Cellular infiltration, as assessed by cytometry in nasal lavage fluid 60min after acute allergen challenge, was reduced by montelukast and heparin but not by antihistamines, L-NAME nor dexamethasone. This pattern of effects of the drugs, given by doses and routes previously described in the literature as being effective was not completely consistent with expected responses. The lack of effect of dexamethasone probably reflects the fact that it was given acutely whereas in the clinic chronic administration is used. The two antihistamines were not identical in their actions, presumably reflecting the fact that cetirizine has therapeutic actions not entirely confined to blockade of H1 receptors. Montelukast has not been reported to have major effects on sneezing and itching in the clinic but reduces nasal obstruction (lower nasal airway pressure or nasal patency). Montelukast's effects on cellular infiltration indicate the possible involvement of leukotrienes. Heparin has actions on inflammatory cell infiltration. This could explain its profile of reducing both cellular infiltration, and increased nasal airway pressure.

Histamine signaling through the H(2) receptor in the Peyer's patch is important for controlling Yersinia enterocolitica infection.

Enteric pathogens such as Yersinia enterocolitica readily colonize and induce disease within the lymphatic tissues of the small intestine. To gain a comprehensive view of the host response to pathogens within these tissues, we determined the transcriptional profiles of intestinal lymphatic tissue infected with Y. enterocolitica. Expression analysis using Affymetrix GeneChips revealed a complex host response in the Peyer's patches and mesenteric lymph nodes after oral infection with Y. enterocolitica. Interestingly, histidine decarboxylase (Hdc) was significantly up-regulated in response to Y. enterocolitica infection. HDC is the enzyme solely responsible for the production of the biogenic amine histamine. Although histamine is well known for its role in allergy and for its effects on immunity and inflammation, little is known about its role or specific histamine receptors during the host response to bacterial infection. In this study, we provide evidence that histamine signaling through the histamine H(2) but not the H(1) receptor is important for controlling Y. enterocolitica infection within the Peyer's patches and mesenteric lymph nodes of mice.

ReN-1869 [(R)-1-(3-(10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ylidene)-1-propyl)-3-piperidine carboxylic acid], a novel histamine H1 receptor antagonist, produces potent and selective antinociceptive effects on dorsal horn neurons after inflammation and neuropathy.

We characterized the effect of a novel selective histamine H1 receptor antagonist, (R)-1-(3-(10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5-ylidene)-1-propyl)-3-piperidine carboxylic acid (ReN-1869), on the responses of dorsal horn neurons in anesthetized rats after carrageenan induced-inflammation and peripheral neuropathy (L5/6 spinal nerve ligation; SNL). ReN-1869 was administered systemically (0.1-4 mg/kg), and drug effects were assessed using a wide range of peripheral electrical and natural stimuli (brush, von Frey filaments, and heat). Comparisons were made between unoperated naive groups and either carrageenan inflamed or SNL rats. ReN-1869 produced little effect on the electrically evoked responses (wind-up, Abeta-, Adelta-, and C-fiber-evoked responses); however, it significantly attenuated neuronal responses to noxious heat in carrageenan and SNL rats. A robust effect was seen with the low-threshold mechanical punctate (von Frey 9 g) stimuli, which were selectively inhibited by ReN-1869 after tissue and nerve injury. These inhibitory actions were in marked contrast to the naive animal group, where only nonsignificant effects were observed. To investigate whether the actions of ReN-1869 are mediated via the antagonism of histamine H1 receptors, the effects of this novel compound were compared with that of another H1 receptor antagonist, mepyramine (1-20 mg/kg). Systemic mepyramine produced strong inhibitions of the 9-g von Frey-evoked responses in carrageenan and SNL rats. The similar pharmacological profile of these two compounds suggests for a similar mechanism of action. We propose that ReN-1869 may represent a novel agent for the treatment of certain modalities of persistent pain states, in particular for the treatment of mechanical allodynia.

Anxiolytic-like effects of escitalopram, citalopram, and R-citalopram in maternally separated mouse pups.

The S-enantiomer of citalopram, escitalopram, is a selective serotonin reuptake inhibitor (SSRI) that appears to be responsible for citalopram's antidepressant and anxiolytic effects. Clinically, escitalopram is reported to have fewer adverse side effects than do other SSRIs. This study compared escitalopram to other antidepressants in a preclinical procedure predicting anxiolytic-like effects of drugs. Carworth Farms Webster (CFW) mouse pups (7 days old) were separated from the dam and maintained at a temperature of 34 degrees C. Forty-five minutes after administering citalopram (0.56-10 mg/kg), escitalopram (0.0056-3 mg/kg), R-citalopram (1-10 mg/kg), paroxetine (0.3-3 mg/kg), fluoxetine (1-30 mg/kg), or venlafaxine (3-56 mg/kg) subcutaneously, the pups were placed individually on a 19.5 degrees C surface for 4 min. Ultrasonic vocalizations (USVs) (30-80 kHz), grid crossing, rolling (i.e., the pup turned on one side or its back), and colonic temperature were recorded. All the drugs reduced USV emission; escitalopram was the most potent (ED(50) 0.05 mg/kg), followed by paroxetine (0.17 mg/kg), citalopram (1.2 mg/kg), fluoxetine (4.3 mg/kg), R-citalopram (6 mg/kg), and venlafaxine (7 mg/kg). The doses that decreased USVs differed from those that increased motor activity. Increased grid crossing occurred after low doses of paroxetine (0.03 or 0.1 mg/kg) and fluoxetine (1 mg/kg), but only after the highest doses of the citalopram enantiomers and venlafaxine (0.3, 10, and 56 mg/kg, respectively). Except for escitalopram and venlafaxine, high doses of the treatments increased rolling. R-Citalopram caused a 10-fold rightward shift in escitalopram's dose-effect curve, suggesting that R-citalopram inhibits escitalopram's anxiolytic-like effects. These data support clinical findings that escitalopram is a potent, well tolerated SSRI with anxiolytic-like effects.

Multiple cedar pollen challenge diminishes involvement of histamine in allergic conjunctivitis of Guinea pigs.

It has been reported that antihistamines do not fully modify symptoms of allergic conjunctivitis in clinical settings, suggesting that histamine is not the only contributor to symptom generation in the disease. However, in the majority of experimental allergic conjunctivitis models, antihistamines are very effective in the reduction of symptoms. In the present study, we used our recently developed guinea pig model of allergic conjunctivitis and evaluated whether involvement of histamine in the induction of symptoms of allergic conjunctivitis is altered by multiple antigen challenges. Guinea pigs were sensitized by intraperitoneal injection of Japanese cedar pollen extracts adsorbed on aluminum hydroxide gel, and then challenged by dropping a pollen suspension without the adjuvant on each eye once a week until the 15th challenge. The magnitude of the conjunctivitis intensity score (CIS), itch-associated scratching response and albumin leakage were found to increase with repeated challenges. At the 1st-3rd challenges, histamine H(1) receptor antagonist, mepyramine (10 mg/kg, p.o.), strongly reduced all these symptoms. However, symptoms at the 5th-15th challenges were not inhibited by mepyramine. On the other hand, a nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (10 mg/kg, i.v.), potently inhibited the increase of CIS and albumin leakage at the 15th challenge. In conclusion, histamine involvement in the induction of conjunctivitis symptoms in our model was diminished by multiple antigen challenges. The allergic conjunctivitis at the chronic stage is partly mediated by nitric oxide (NO) derived from NOSs that may be activated by mediators other than histamine. The histamine-independent allergic conjunctivitis may be useful for analyzing mechanisms underlying chronic conjunctivitis.

Pharmacological characterization of mouse hind paw oedema induced by Bothrops insularis (jararaca ilhoa) snake venom.

Bothrops snake venoms produce marked local effects, including oedema, haemorrhage and necrosis. The ability of Bothrops insularis venom to induce oedema in mice was investigated. Venom was injected into hind paws and the change in volume over time was measured by plethysmometry. B. insularis venom (0.01-2.5 microg/paw) induced paw oedema which, at high doses (>/=0.5 microg/paw), was accompanied by haemorrhage. The peak oedematogenic response occurred 3 h after venom injection with all doses and decreased gradually thereafter, but was still elevated with high doses after 24 h. Pretreating the mice with cyproheptadine (histamine H(1) and serotonin 5-HT(2) receptor antagonist), mepyramine (histamine H(1) receptor antagonist), L-NAME (inhibitor of nitric oxide synthase), indomethacin and rofecoxib (inhibitors of cyclooxygenases), and dexamethasone (indirect inhibitor of PLA(2)) significantly attenuated venom-induced oedema, whereas methysergide, a serotonin 5-HT(1)/5-HT(2) receptor antagonist, had no effect. The administration of antivenom 30 min before or immediately after venom injection also significantly inhibited venom-induced oedema. These results show that B. insularis venom causes oedema in the mouse hind paw and that this response is mediated by histamine, nitric oxide, and arachidonic acid metabolites formed by cyclooxygenases 1 and 2. The neutralization by commercial antivenom indicates that the venom components responsible for oedema are recognized by the antivenom and share immunological identity with their counterparts in the venoms of mainland Bothrops species.

Suppression of spontaneous scratching in hairless rats by sedatives but not by antipruritics.

Experimental scratching in animals has hitherto been provoked by substances injected into the skin or central nervous system. We aimed to investigate if spontaneous scratching in the rat can be reduced by sedatives and antipruritics, and to assess if spontaneous scratching is elicited from the skin or the central nervous system. It may also be a complex behaviour related to the rat species, different from clinical itch. Eight male hairless rats were studied for 6 weeks. The animals were recorded on videotape in the middle of the day and at night, and the scratching activity was counted. The following substances were tested sequentially: midazolam, mepyramine, a eutectic mixture of lignocaine and prilocaine (EMLA, betamethasone dipropionate and a vehicle. On days 1-3 of each sequence, the test material was applied to a 42-cm(2) area on the rostral part of the back. Subsequent treatment of the whole body was made on day 4. Midazolam was injected intraperitoneally from day 1 to day 4. After 4 days of treatment, there was a wash-out phase of 3 days until the next sequence. We found a positive correlation between minutes awake and number of scratch episodes. Spontaneous scratching was lower after mepyramine on day 4 (p = 0.046) and after midazolam injections on days 1-3 (p = 0.009) and day 4 (p = 0.003). The local anaesthetic, EMLA, did not significantly influence spontaneous scratching. In conclusion, only the drugs with sedative properties suppressed spontaneous scratching, which is probably a cerebral phenomenon or otherwise explained general behaviour, rather than a reaction to skin stimuli. Thus, for testing of topically applied antipruritics, spontaneous scratching cannot be used as an animal model. Furthermore, evaluation of provocative scratching should eliminate/exclude spontaneous scratching.

Characterization of nasal obstruction in the allergic guinea pig using the forced oscillation method.

INTRODUCTION: This is the first report to evaluate changes in nasal resistance in a preclinical animal model using the forced oscillation method. METHODS: The method involves characterizing pressure-flow relationships of the respiratory system due to external oscillatory forces. RESULTS: First, we evaluated changes in nasal resistance using an established small-animal rhinometric technique. In these studies, aerosolized ovalbumin (3%) administered to the nasal cavity of ovalbumin-sensitized guinea pigs increased nasal resistance at 30 min by 99 +/- 14%. The histamine H1 antagonists, chlorpheniramine (1 mg/kg i.v.) and pyrilamine (1 mg/kg i.v.), blocked the increase in nasal resistance due to ovalbumin provocation (50 +/- 17% and 39 +/- 11% over baseline, respectively). The alpha-adrenergic agonist phenylpropanolamine (3 mg/ kg i.v.) had no effect on the nasal actions of ovalbumin. In separate studies, nasal resistance was measured at 2 Hz by forced oscillation and ovalbumin (3%) increased nasal resistance by 91 +/- 14%. Chlorpheniramine (1 mg/kg i.v.) significantly attenuated the increase in nasal resistance due to ovalbumin. Finally, changes in nasal resistance for each treatment group were evaluated at frequencies of 1 - 18 Hz. Area under the curve analysis demonstrated that chlorpheniramine blocked the nasal obstructive effect of ovalbumin. In contrast, a pharmacologically active dose of phenylpropanolamine (3 mg/kg i.v.) did not produce decongestant activity. DISCUSSION: The current data are inconsistent with the well-established clinical efficacy of alpha-adrenergic agonists as nasal decongestants. Consequently, we suggest that allergic nasal obstruction in the guinea pig may not be the best preclinical approach to assess the nasal decongestant activity of vasoconstrictor alpha-adrenergic agonists. Additionally, our studies demonstrate the utility of the forced oscillation technique in assessing changes in nasal resistance in small laboratory animals.