Intranasal Pressure Research Articles

Phantosmia as a meteorological forecaster

In normosmics, olfactory ability has been found to vary with ambient humidity, barometric pressure, and season. While hallucinated sensations of phantom pain associated with changes in weather have been described, a linkage to chemosensory hallucinations has heretofore not been reported. A 64-year-old white male with Parkinson's disease presents with 5years of phantosmia of a smoky burnt wood which changed to onion-gas and then to a noxious skunk-onion excrement odor. Absent upon waking it increases over the day and persists for hours. When severe, there appears a phantom taste with the same qualities as the odor. It is exacerbated by factors that manipulate intranasal pressure, such as coughing. When eating or sniffing, the actual flavors replace the phantosmia. Since onset, he noted the intensity and frequency of the phantosmia forecasted the weather. Two to 3h before a storm, the phantosmia intensifies from a level 0 to a 7-10, which persists through the entire thunderstorm. Twenty years prior, he reported the ability to forecast the weather, based on pain in a torn meniscus, which vanished after surgical repair. Extensive olfactory testing demonstrates underlying hyposmia. Possible mechanisms for such chemosensory-meteorological linkage includes: air pressure induced synesthesia, disinhibition of spontaneous olfactory discharge, exacerbation of ectopic discharge, affect mediated somatic sensory amplification, and misattribution error with expectation and recall bias. This is the first reported case of weather-induced exacerbation of phantosmia. Further investigation of the connection between chemosensory complaints and ambient weather is warranted.

Intranasal pressure splints - a reliable alternative to nasal packing in septal sur

Objective: To compare the outcome of nasal packing and intranasal pressure splints in patients undergoing septoplasty. Study design: Randomized controlled trial.Place and Duration of Study: The study was carried out at otorhinolaryngology department of Combined Military Hospitals, Bahawalpur and Murree from June 2010 to November 2011.Methods: A total of 160 patients aged 15 to 50 years, undergoing septoplasty, were included in the study and distributed in two equal groups. Group A with nasal packing, was compared with group B in which nasal splints were placed and no nasal packing was done. Post operative morbidity in terms of pain, headache, epiphora, dysphagia and sleep disturbance along with post operative complications including nasal bleed, septal hematoma and synechiae formation were assessed over a follow up period of four weeks.Results: Patients in which nasal packing was done had significantly more post operative pain (p < 0.05) and a significantly higher incidence of headache, epiphora, dysphagia and sleep disturbance on the night of surgery (p < 0.05). There was no significant difference between two groups with respect to nasal bleeding, septal hematoma and synechiae formation.Conclusion: Pressure splints around nasal septum are effective alternative to nasal packing. With the use of these splints, nasal packing can be easily avoided following septal surgery, thus minimizing post operative discomfort of the patient. DOI: http://dx.doi.org/10.3329/bjo.v18i2.11985 Bangladesh J Otorhinolaryngol 2012; 18(2): 124-128

The Potential Role of Prostaglandin D2 in Nasal Congestion Observed in a Guinea Pig Model of Allergic Rhinitis

Background: Allergic rhinitis is the most common allergic disease, displaying the typical nasal symptom of congestion. Prostaglandin D₂ (PGD₂), a chemical mediator released in large amounts by mast cells upon allergic stimulation in humans, is known to be involved in nasal congestion. However, the mechanism by which this congestion occurs remains unclear. Methods: The effect of PGD₂ on the nasal airflow in guinea pigs was measured using a noninvasive approach that avoided any anesthetic effect. Isometric tension of isolated nasal mucosa and the nasal vascular corrosion resin cast technique were used to clarify the area of nasal mucosal vessels affected by PGD₂, and to examine the mechanism of PGD₂-induced nasal congestion. Moreover, the involvement of second messengers in PGD₂-induced mucosal relaxation was investigated. Results: PGD₂ induced an increase in intranasal pressure in a guinea pig model of rhinitis. Additionally, sinusoidal microvessel dilatation appeared around the septum using the vascular corrosion resin cast technique in the nasal mucosa. Moreover, relaxation of the nasal mucosa following stimulation of the prostanoid DP-1 receptor was associated with cAMP levels in the tissue. Conclusions: PGD₂-induced nasal congestion is caused by direct dilatation of the sinusoid vessels through the increase of cAMP levels in the nasal mucosa, demonstrating that the mechanism of PGD₂-induced nasal congestion is different from other chemical mediators. Consequently, antagonists for the prostanoid DP-1 receptor would be an alternative approach for the relief of nasal congestion. Alternatively, the combined administration with antagonists for other mediators involved in nasal congestion may also be a valuable therapy for allergic rhinitis.

The relationship between pressure and volume when using Rapid Rhino(r) packs in the management of epistaxis

Despite the popularity of Rapid Rhino packs, there are no clear guidelines regarding the volume of air to be inflated when used in the management of epistaxis. The manufacturers suggest that subjective assessment by pilot cuff palpation is used to guide inflation. However, studies have clearly demonstrated that clinicians are poor at judging balloon pressure by pilot cuff palpation when used in other settings. Our objective was to investigate the relationship between the volume of air inflated and the resultant intra-nasal pressure generated by nasal balloon packing. Twelve healthy subjects were packed with 5.5 cm Rapid Rhino packs, which were connected to a manometer and 20 ml syringe via a 3-way tap in a closed circuit. Increments of 2.5 mls of air were inflated and the resultant intra-nasal pack pressure was measured. There appeared to be a linear relationship between increasing volume and pack pressure. However, between individuals, there was a large variation in the intra-nasal pack pressure produced for a given fixed volume of air inflated. This is presumably due to variations in nasal anatomy. It may be that a manometer-measured, pressure guided nasal pack inflation technique would represent best practice, especially for less experienced staff.

Predictors of Response to a Nasal Expiratory Resistor Device and Its Potential Mechanisms of Action for Treatment of Obstructive Sleep Apnea

A one-way nasal resistor has recently been shown to reduce sleep disordered breathing (SDB) in a subset of patients with Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS). The purpose of this study was to examine characteristics predictive of therapeutic response to the device and provide pilot data as to its potential mechanisms of action. PATIENTS, INTERVENTIONS, AND MEASUREMENTS: 20 subjects (15M/5F, age 54 ± 12 years, BMI 33.5 ± 5.6 kg/m²) with OSAHS underwent 3 nocturnal polysomnograms (NPSG) including diagnostic, therapeutic (with a Provent® nasal valve device), and CPAP. Additional measurements included intranasal pressures and PCO₂, closing pressures (Pcrit), and awake lung volumes in different body positions. In 19/20 patients who slept with the device, RDI was significantly reduced with the nasal valve device compared to the diagnostic NPSG (27 ± 29/h vs 49 ± 28/h), with 50% of patients having an acceptable therapeutic response. Among demographic, lung volume, or diagnostic NPSG measures or markers of collapsibility, no significant predictors of therapeutic response were found. There was a suggestion that patients with position-dependent SDB (supine RDI > lateral RDI) were more likely to have an acceptable therapeutic response to the device. Successful elimination of SDB was associated with generation and maintenance of an elevated end expiratory pressure. No single definitive mechanism of action was elucidated. The present study shows that the nasal valve device can alter SDB across the full spectrum of SDB severity. There was a suggestion that subjects with positional or milder SDB in the lateral position were those most likely to respond.

Correlation between Pressure Sensitivity of Nasal Mucosa and Experimentally Induced Nasal Stuffiness in Healthy Adults

Background and ObjectivesZZThe correlation between subjective nasal obstruction symptom and minimal cross-sectional area (MCA) of nasal cavity is uncertain. Some chemicals change subjective nasal obstruction symptoms without changing MCA. The aim of this study is to evaluate the correlation between the tactile pressure sense of nasal mucosa and the nasal obstruction symptom. Subjects and MethodZZFrom 30 healthy adult volunteers, sensitivity to pressure change (P-sensitivity) and sensitivity to MCA change (A-sensitivity) were measured for each side of the nose, respectively. P-sensitivity was obtained as the slope of the regression line which was defined as the change of visual analog scale (VAS) score of the subjective nasal pressure sense divided by the change of inflated intranasal balloon pressure. A-sensitivity was obtained as the slope of the regression line which was defined as the change of VAS score of nasal obstruc tion divided by the change of MCA measured with acoustic rhinometry in experimentally narrowed or blocked nose using pieces of sponge. ResultsZZThere was a strong correlation between P-sensitivity and A-sensitivity. In each volunteer, P-sensitivity or A-sensitivity of one side nose was well correlated with those of the opposite side, respectively. ConclusionZZBoth P-sensitivity and A-sensitivity of human nose vary from person to person, but they have a strong correlation with each other. Nasal obstruction symptom can be influ enced by change of general somatic sense of nasal mucosa. � Korean J Otorhinolaryngol-Head Neck Surg 2011;54:623-8 Key WordsZZAcoustic rhinometry ㆍNasal obstruction ㆍSensation.

Aerodynamic effects of inferior turbinate surgery on nasal airflow--a computational fluid dynamics model

Turbinate reduction surgery may be indicated for inferior turbinate enlargement when conservative treatment fails. The aim of this study was to evaluate the effects of inferior turbinate surgery on nasal aerodynamics using computational fluid dynamics (CFD) simulations. CFD simulations were performed for the normal nose, enlarged inferior turbinate and following three surgical procedures: (1) resection of the lower third free edge of the inferior turbinate, (2) excision of the head of the inferior turbinate and (3) radical inferior turbinate resection. The models were constructed from MRI scans of a healthy human subject and a turbulent flow model was used for the numerical simulation. The consequences of the three turbinate surgeries were compared with originally healthy nasal model as well as the one with severe nasal obstruction. In the normal nose, the bulk of streamlines traversed the common meatus adjacent to the inferior and middle turbinate in a relatively vortex free flow. When the inferior turbinate was enlarged, the streamlines were directed superiorly at higher velocity and increased wall shear stress in the nasopharynx. Of the three surgical techniques simulated, wall shear stress and intranasal pressures achieved near-normal levels after resection of the lower third. In addition, airflow streamlines and turbulence improved although it did not return to normal conditions. As expected, radical turbinate resection resulted in intra-nasal aerodynamics of atrophic rhinitis demonstrated in previous CFD studies. There is little evidence that inspired air is appropriately conditioned following radical turbinate surgery. Partial reduction of the hypertropic turbinate results in improved nasal aerodynamics, which was most evident following resection of the lower third. The results were based on a single individual and cannot be generalised without similar studies in other subjects.

A review of the implications of computational fluid dynamic studies on nasal airflow and physiology

Computational fluid dynamics has been adapted to studying nasal aerodynamics. To review current literature on CFD studies, with an emphasis on normal nasal airflow, the impact of sinonasal pathology on airflow, and implications on nasal physiology. The objective is to provide the rhinologists with a greater understanding of nasal airflow and how symptomatology of sinonasal disease may be explained via CFD simulations. The nasal valve region redirects inspiratory airstreams over the inferior turbinate in a high turbulent kinetic energy, which is important in heat and moisture exchange. The bulk of airflow occurs in the common meatus with small streams traversing the olfactory groove, increasing during sniffing. Septal deviation and enlarged inferior turbinate causes redistribution of airflow, changes in intranasal pressure and increased turbulence. High velocity airflow and wall shear stress at the septal perforation causes desiccation and mucosal damage. The airflow within an atrophic nasal cavity is predominantly laminar with minimal contact with nasal mucosa. The inferior turbinate is an important organ for air conditioning and preservation during surgery is highlighted. Despite some limitations of CFD simulations, this technology has improved understanding of the complex nasal anatomy and the implications of disease and surgery on physiology.

A Method for Generating Natural and User-Defined Sniffing Patterns in Anesthetized or Reduced Preparations

Sniffing has long been thought to play a critical role in shaping neural responses to odorants at multiple levels of the nervous system. However, it has been difficult to systematically examine how particular parameters of sniffing behavior shape odorant-evoked activity, in large part because of the complexity of sniffing behavior and the difficulty in reproducing this behavior in an anesthetized or reduced preparation. Here we present a method for generating naturalistic sniffing patterns in such preparations. The method involves a nasal ventilator whose movement is controlled by an analog command voltage. The command signal may consist of intranasal pressure transients recorded from awake rats and mice or user-defined waveforms. This "sniff playback" device generates intranasal pressure and airflow transients in anesthetized animals that approximate those recorded from the awake animal and are reproducible across trials and across preparations. The device accurately reproduces command waveforms over an amplitude range of approximately 1 log unit and up to frequencies of approximately 12 Hz. Further, odorant-evoked neural activity imaged during sniff playback appears similar to that seen in awake animals. This method should prove useful in investigating how the parameters of odorant sampling shape neural responses in a variety of experimental settings.

Sniffing Behavior of Mice during Performance in Odor-Guided Tasks

Sniffing, a rhythmic inhalation and exhalation of air through the nose, is a behavior thought to play a critical role in shaping how odor information is represented and processed by the nervous system. Although the mouse has become a prominent model for studying olfaction, little is known about sniffing behavior in mice. Here, we characterized mouse sniffing behavior by measuring intranasal pressure transients in behaving mice. Sniffing was monitored during unstructured exploratory behavior and during performance of 3 commonly used olfactory paradigms: a habituation/dishabituation task, a sand digging-based discrimination task, and a nose poke-based discrimination task. We found that respiration frequencies in quiescent mice ranged from 3 to 5 Hz--higher than that reported for rats. During exploration, sniff frequency increased up to approximately 12 Hz and was highly dynamic, with rapid changes in frequency, amplitude, and waveform. Sniffing behavior varied strongly between tasks as well as for different behavioral epochs of each task. For example, mice performing the digging-based task showed little increase in sniff frequency prior to digging, whereas mice performing a nose poke-based task showed robust increases. Mice showed large increases in sniff frequency prior to reward delivery in all tasks. Mice also showed increases in sniff frequency when nose poking in a nonodor-guided task. These results show that mouse sniffing behavior is highly dynamic, varies with behavioral context, and is strongly modulated by olfactory as well as nonolfactory events.

Preclinical Efficacy and Safety Pharmacology of SUN-1334H, a Potent Orally Active Antihistamine Agent

These studies aimed to outline the in vitro and in vivo histamine H(1) receptor antagonistic activity and safety pharmacology of SUN-1334H, a new potent antihistamine agent under clinical development. In vitro antihistamine activity and selectivity of SUN-1334H was evaluated in a panel of receptor and enzyme assays and functional assays using isolated tissues. In vivo antihistamine and antiallergy efficacy were assessed following oral administration of SUN-1334H in histamine-induced bronchoconstriction in guinea pigs, skin wheal in beagle dogs and ovalbumin-induced rhinitis (sneezing, vascular permeability and intranasal pressure) in guinea pigs. Cardiovascular safety was assessed by CHO-K1/human ether-à-go-go related gene (hERG) K(+) current assay, dog telemetry and guinea-pig ECG. CNS safety was assessed by functional observational battery in rats and pentobarbital-induced sedation and pentylenetetrazol-induced convulsions in mice. The effect on intestinal motility was assessed in rats. In vitro receptor binding assays showed that SUN-1334H had high histamine H(1) receptor binding affinity with an inhibition constant value of 9.7 nmol/L and either no or insignificant affinity with a panel of receptors and enzymes. In functional assays, SUN-1334H caused potent inhibition of histamine-induced contractions of isolated guinea-pig ileum with an IC(50) (half the maximal inhibitory concentration) of 0.198 micromol/L. In contrast, SUN-1334H had no significant effect on isolated tissue contractions induced by cholinergic, H(2)-histaminergic, serotonergic, adrenergic receptor agonists or BaCl(2). In studies of animal models of histamine-mediated disorders, SUN-1334H potently inhibited histamine-induced bronchospasm over 24 hours following oral administration and completely suppressed histamine-induced skin wheal in beagle dogs and ovalbumin-induced rhinitis in guinea pigs. In CHO-K1/hERG cells, SUN-1334H did not modulate hERG K(+)-currents at concentrations as high as 100 micromol/L. Cardiovascular and CNS function and intestinal motility were not altered at doses several-fold greater than those required for efficacy, indicating a good safety profile of the drug. SUN-1334H is a potent, orally active, highly selective H(1) receptor antagonist with a long duration of action in its preclinical profile. It has potential for the treatment of disorders involving histamine as a mediator.

Sexually dimorphic enhancement by estradiol of male urinary odor detection thresholds in mice.

We asked whether sex and adult estrogen exposure influence the detection thresholds for urinary odors used by mice to guide their social behaviors. Gonadectomized (GDX) male and female mice were trained on a two-choice food-motivated task to determine detection thresholds for male urinary odors. There was no significant sex difference in the detection of these odors by GDX subjects without hormone replacement. However, during treatment with estradiol benzoate (EB), GDX females, but not GDX males, showed an enhanced ability to detect these odors. To investigate a possible mechanism for this effect, the authors measured GDX females' odor-sampling behavior (sniffing) by monitoring intranasal pressure transients during performance of the urinary odor detection task with and without EB treatment. Under both hormone conditions, females decreased their sniffing frequency as the urinary odor concentration decreased, with this decrease being significantly greater while GDX females received EB. Thus, estradiol enhanced detection thresholds for male urine in a sex-specific manner, and this enhanced sensitivity in females was correlated with altered odor-sampling behavior.

Contribution of prostaglandin D 2 via prostanoid DP receptor to nasal hyperresponsiveness in guinea pigs repeatedly exposed to antigen

We examined the role of prostanoid DP receptor in nasal blockage in an experimental allergic rhinitis model in guinea pigs. Local inhalation of prostaglandin D 2 (PGD 2) to the nasal cavity resulted in an increase in intranasal pressure in guinea pigs actively sensitized by repeated antigen exposure but not in non-sensitized guinea pigs. Nasal hyperresponsiveness was observed when the guinea pigs were exposed to histamine and U-46619 (11α, 9α-epoxymethano-PGH 2; a thromboxane (TX) A 2 mimetic) after repeated antigen exposure. S-5751 ((Z)-7-[(1R,2R,3S,5S)-2-(5-hydroxybenzo[b]thiophen-3-ylcarbonylamino)-10-norpinan-3-yl]hept-5-enoic acid), a prostanoid DP receptor antagonist, inhibited not only PGD 2-induced nasal blockage but also nasal hyperresponsiveness to histamine and U-46619 in sensitized guinea pigs. Combined exposure of the nasal cavity of guinea pigs to an aerosol of PGD 2 with histamine or U-46619 at sub-threshold concentrations synergistically caused a marked increase in intranasal pressure. These responses were significantly suppressed by S-5751. These results suggest that PGD 2 plays a critical role in the increase in intranasal pressure via prostanoid DP receptor, probably through synergistically enhancing the nasal response with other chemical mediators released from mast cells and other inflammatory cells activated by allergens.

Severe Orbitopalpebral Emphysema after Nose blowing Requiring Emergency Decompression

Orbital emphysema is a frequent condition associated with medial wall fractures after blunt trauma. It is usually a benign, self-limited phenomenon. The authors are unaware of previous reports of severe orbital emphysema needing emergency decompression with no evidence of any previous significant trauma such as the case presented herein. A 51-year-old woman had painful swelling of the left orbital region that prevented her from opening her eyelids. She complained of a coincident cold with abundant mucous rhinorrhea. She had blown her nose vigorously several times. A computed tomography scan revealed a left proptosis, an extensive orbitopalpebral emphysema, and a blowout fracture of the medial wall of the left orbit. A complete ophthalmic examination was only possible after a needle decompression. No significant ocular damage was observed, so outpatient treatment was provided. Twenty-eight hours later, the swelling had almost disappeared, and the ocular assessment was normal. A forceful expiratory effort raising intranasal pressure may cause a medial wall orbital fracture. If the airway hyperpressure episodes are repeated, a severe orbitopalpebral emphysema may develop. Should there be any suspicion of vascular compression, it must be drained to allow the assessment of visual function and theoretically prevent a potentially irreversible ischemic visual loss.

The Nasal Valve: A Review of the Anatomy, Imaging, and Physiology

The nasal valve region has remained difficult to define in clinical practice in part because of lack of integration between physiological data and anatomic-surgical findings. In this review, we summarize the anatomic, physiological, and imaging data regarding this complex area of airflow regulation. There is no singular resistive focus or singular valve structure to explain all of the reported findings. We conclude that there is a nasal valve region that begins approximately at the limen nasi and continues for several millimeters within the nasal cavum beyond the piriform aperture. Intranasal pressure measurements reflect distributed resistance across this nasal valve region. The geometry and anatomic constitution of the nasal valve region change greatly from its entrance to its distal aspect. To refer consistently to the component portions of the nasal valve region, we suggest the terms cartilaginous valve segment and bony valve segment for use in reporting future studies.

Effects of TAK-427 on acute nasal symptoms and nasal obstruction in guinea pig model of experimental allergic rhinitis

TAK-427 {2-[6-[[3-[4-(diphenylmethoxy)piperidino]propyl]amino]imidazo[1,2- b]pyridazin-2-yl]-2-methylpropionic acid dihydrate} is a novel anti-allergic agent that has both histamine H 1-receptor antagonist and anti-inflammatory activities. In this study, we evaluated the efficacy of TAK-427 on acute nasal responses and nasal obstruction using various guinea pig models of allergic rhinitis. TAK-427 inhibited the histamine-induced nasal reactions with an ID 50 value of 0.633 mg/kg, p.o. TAK-427 (0.1–10 mg/kg, p.o.) and most histamine H 1-receptor antagonists tested inhibited the increase in intranasal pressure, nasal hypersecretion, sneezing and nasal itching caused by a single antigen challenge in sensitized guinea pigs. In addition, TAK-427 (0.3, 30 mg/kg, p.o.) significantly inhibited the development of nasal obstruction when sensitized guinea pigs were repeatedly challenged via inhalation with Japanese cedar pollen, whereas the histamine H 1-receptor antagonist, azelastine (1 mg/kg, p.o.), and ketotifen (1 mg/kg, p.o.) were without effect. These results suggest that TAK-427 might not only suppress acute nasal symptoms but also ameliorate nasal obstruction via the effects other than those as a histamine H 1-receptor antagonist.

Yamik Sinus Catheter in the Topical Treatment of Patients with Acute Rhinosinusitis after Previous Sinus Surgery

The Yamik sinus catheter was designed as a new device for the topical treatment of rhinosinusitis. It creates intermittent positive and negative intranasal pressure after sealing the ipsilateral nostril and choana with two inflatable cuffs. Affecting the nasal cavity and all paranasal sinuses of one side at a time, it is used to evacuate mucous and secretions as well as and to introduce antiseptic, antibacterial, or antifungal solutions. This study was designed to evaluate the effectiveness of the Yamik catheter in cases of acute purulent rhinosinusitis in patients who previously underwent endonasal sinus surgery for chronic rhinosinusitis. Twenty patients were treated at repeated visits to the outpatient clinic of our institution. At each visit, their clinical symptoms as well as findings on anterior rhinoscopy, nasal endoscopy, and A-mode ultrasound were evaluated. Acute disease resolved completely within 10 days of treatment in 17 of the 20 patients. Two patients discontinued treatment after repeated visits, showing only mild improvement. One patient felt uncomfortable during the application of the Yamik catheter and did not continue after the initial treatment. Our results suggest that the Yamik catheter may be a helpful device in the topical treatment of acute rhinosinusitis and it appears possibly helpful in patients who suffer from episodes of acute purulent infection after previous sinus surgery.

Elevated Nasal Mucosal G Protein Levels and Histamine Receptor Affinity in a Guinea Pig Model of Nasal Hyperresponsiveness

Background: Nasal hyperresponsiveness is a common feature of allergic rhinitis, but the underlying mechanisms have yet to be elucidated. The effects of repeated antigen inhalation on the characteristics of histamine H₁ receptors and expression levels of heterotrimeric guanosine 5′-triphosphate-binding proteins in nasal mucosa were investigated to understand the mechanisms of the pathogenesis of nasal hyperresponsiveness in allergic rhinitis. Methods: Male Hartley guinea pigs were sensitized by the inhalation of dinitrophenylated ovalbumin antigen (10 mg of protein/ml) and repeatedly challenged by inhaling aerosolized dinitrophenylated ovalbumin antigen for 3 weeks. Twenty-four hours after the last antigen inhalation, in vivo nasal responsiveness to histamine was measured. [³H]Mepyramine binding assays and immunoblotting for α subunits of the G_q protein were also performed using membrane preparations of isolated nasal mucosae. Results: The histamine-induced increase in intranasal pressure was significantly augmented after repeated antigen challenge, indicating that nasal hyperresponsiveness was achieved. In saturation binding studies, no significant change was observed in the density and antagonist affinity of H₁ receptors in the hyperresponsive animals. On the other hand, the affinity of histamine for high-affinity agonist binding sites in the hyperresponsive group, measured by histamine competition binding studies, was much greater than that in control animals, and these results were affected by guanosine 5′-O-(3-thiotriphosphate) in both groups. Moreover, Gα_q levels in nasal mucosal homogenates were significantly increased after repeated antigen challenge. Conclusions: Elevated G protein levels in nasal mucosa might induce an increased binding affinity of histamine to its receptors, resulting in an augmented nasal response to histamine, that is, nasal hyperresponsiveness, in guinea pigs.

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Involvement of thromboxane A2 in antigen-induced nasal blockage in guinea pigs.

To estimate the involvement of thromboxane (Tx) A2 in the onset of nasal blockage, we examined the effect of the selective TxA2 receptor antagonist, S-1452, as well as an H1-antihistamine, diphenhydramine, on the antigen-induced increase in intranasal pressure, as an index of nasal blockage, in anesthetized guinea pigs actively sensitized by inhalation of aerosolized ovalbumin (OA). Oral administration of S-1452 or intravenous administration of diphenhydramine significantly but incompletely reduced the increase in intranasal pressure following exposure of the nasal cavity of guinea pigs to aerosolized OA. In combination, the two agents were more effective than either alone, but there was no significant difference between them. The TxB2 level was significantly elevated in nasal lavage fluid 15 and 30 min after antigen challenge. Exposure of the nasal cavity of guinea pigs to aerosolized U-46619, a TxA2 mimetic, also resulted in a marked increase in intranasal pressure, and this could be almost completely suppressed by S-1452. These findings suggest that TxA2 contributes to antigen-induced nasal blockage in guinea pigs.