Sympathetic vascular control of the pig nasal mucosa: adrenoceptor mechanisms in blood flow and volume control

Intranasal Application of the α2-Adrenoceptor Agonist BHT-920 Produces Decongestion in the Cat

The effect of α2-selective adrenoreceptor activation on nasal cavity dimension in an experimental model of congestion has not been defined. Presently, we used acoustic rhinometry to evaluate the decongestant activity of BHT-920, a selective α2-adrenergic agonist against nasal congestion produced by intranasal compound 48/80. Administration of the mast cell liberator compound 48/80 (1%) into a nasal passageway decreased ipsilateral volume and minimum cross-sectional area by 73 ± 4% and 42 ± 6%, respectively. The congestant effect of compound 48/80 was blocked by topical BHT-920 (0.3 and 1%) in a dose related manner. In addition, the decrease in minimum cross-sectional area produced by compound 48/80 was attenuated after topical BHT-920 treatment. As a comparison we also evaluated the topical decongestant activity effects of the α1-adrenergic agonist phenylephrine, and the nonselective α-agonist oxymetazoline. Both phenylephrine (0.1–1.0%) and oxymetazoline (0.01–0.3%) produced decongestion. The blood pressure effects of these three drugs also were evaluated. At doses of 0.3 and 1.0%, BHT-920 did not produce hypertension. In contrast, oxymetazoline (0.01–0.1%) produced a transient hypertension that peaked at 15 minutes and fully recovered 45 minutes after administration. The hypertensive effect of phenylephrine at 0.3 and 1.0% lasted over 60 minutes. The present findings indicate that selective α2-agonists may produce decongestant activity with an improved cardiovascular profile compared with current sympathomimetic drugs such as phenylephrine.

The Effect of Topical Xylometazoline on the Mucosal Temperature of the Nasal Septum

Background

The purpose of this study was to determine the short-term influence of the α2-adrenoreceptor agonist xylometazoline on the nasal mucosal temperature.

Methods

Thirty healthy subjects were enrolled into the study. Fifteen of these subjects got xylometazoline and 15 subjects, matched to age, got saline solution as control. A miniaturized thermocouple was used for continuous detection of the septal mucosal temperature without interruption of nasal breathing before and after application of nose spray.

Results

In the anterior nasal segment, the mucosal temperatures before decongestion were significantly higher than after decongestion (p < 0.05). These changes could not be found in the control group after saline solution. The mean end-expiratory mucosal temperatures were significantly higher than the end-inspiratory ones in both study groups (p < 0.005).

Conclusions

The reduction of the nasal mucosal blood flow because of vasoconstriction and the increase of the nasal cavity volume after decongestion with xylometazoline seem to cause a significant decrease of the septal mucosal temperature in the anterior nasal segment. This might be one possible causative factor of the common symptom of the “dry nose” in patients with nasal decongestant abuse.

Role of α2-adrenoceptors in electrical field stimulation-induced contraction of pig nasal mucosa and pharmacologic characterization of a novel α2C-adrenoceptor agonist

BACKGROUND

Blood vessels of the nasal mucosa are richly innervated by sympathetic nerves and neural mechanism is of great interest in upper respiratory tract disorders. This study was designed to determine the role of α2-adrenoceptors and, more specifically, α2C-adrenoceptors, on neurogenic sympathetic vasoconstrictor responses in pig nasal mucosa, and to define the pharmacologic profile of a novel selective α2C-adrenoreceptor agonist.

METHODS

Electrical field stimulation (EFS) was applied to nasal mucosa strips placed in an organ bath and attached to force displacement transducers for continuous recording of isometric tension. The affinity and functional activity of compound B for α2C-adrenoceptors were determined by binding analysis and the ability of compound B to stimulate [(35)S]GTPγS binding to the receptors. Compound B was also tested in a postjunctional α2C-adrenoreceptor bioassay.

RESULTS

EFS-induced contractions were partly blocked by the α2-adrenoreceptor antagonist yohimbine (41.1%) and the α2C-adrenoreceptor antagonist JP-1302 had no effect. The α2-adrenoreceptor agonist clonidine, but not compound B, exerted a significant blockade (70.6%). Compound B had high affinity (K(i) = 18 nM), produced potent agonist (EC50 = 279 nM) and good efficacy (E(max) = 73%) responses at the α2C-adrenoceptors, and displayed good functional agonist potency in the human saphenous vein α2C-adrenoreceptor bioassay (pD2 = 6.2).

CONCLUSION

(1) Neurogenic vasomotor contractility is largely regulated through an α-adrenergic mechanism; (2) pig nasal mucosa possesses post- and prejunctional α2-adrenoceptors; (3) the α2C-adrenoreceptor subtype does not seem to be involved; and (4) compound B is a novel, highly selective, and potent α2C-adrenoreceptor agonist.

Influence of intranasal sterile isotonic sea water applications on xylometazoline administration: an experimental study in pigs

OBJECTIVE

The aim of this study was to investigate how isotonic sea water solution (Physiomer) affects the structure of porcine nasal mucosa when it is applied simultaneously with vasoconstrictors (xylometazoline) for a prolonged period of time.

METHODS

Twenty pigs of the PMR-Landraze breed formed the study group. A solution of xylometazoline 0, 1% (Otrivin spray, Novartis) was sprayed every 8h in both nasal cavities of the pigs, with two applications into each nostril for 28 days. Between the applications (4h later), the right nasal cavity was washed with sterile isotonic sea water (Physiomer Normal, Geomar). Biopsies were taken under endoscopic guidance from the nasal mucosa of each nasal cavity separately at specific times. Five histological parameters were microscopically examined for each biopsy section: (1) inflammation, (2) fibrosis, (3) metaplasia of the epithelium, (4) reactive atypia of the epithelium and (5) necrosis.

RESULTS

Statistically significant differences regarding grade of inflammation on days 7 (p=0.0009), 12 (p=0.01), 20 (p=0.02) and 28 (p=0.0005), regarding grade of fibrosis on day 28 (p=0.026) and regarding epithelial metaplasia on day 5 (p=0.052) were found between the nasal mucosa treated only with vasoconstrictors and the nasal mucosa treated with vasoconstrictors and sea water washing. In all cases, samples from the nasal cavities that had been washed with Physiomer appeared with a lower grade of inflammation, fibrosis and metaplasia compared to the samples from nasal mucosa where no nasal washing was performed.

CONCLUSION

Nasal irrigations with isotonic sea water, when are applied 4h after vasoconstrictors for a long period of time, prevent nasal mucosa from histological damage.

Mechanism of decongestant activity of alpha 2-adrenoceptor agonists

The vascular bed in nasal mucosa of different species, including human, is highly vascularized and an extensive sinusoidal network of large capacitance vessels is present deep within the submucosa. When this network of venous sinusoids is engorged with blood, the swollen mucosa reduces the size of the airway lumen and congestion ensues. Nasal vasculature tone is strongly influenced by the sympathetic nervous system and the only drugs approved specifically to relieve vascular nasal obstruction are alpha-adrenoceptor sympathomimetic agents. Due to their vasoconstrictor action, the sympathomimetic decongestants oppose vasodilation, reducing nasal airway resistance and thus facilitating nose breathing. However, standard decongestants that are non-selective alpha-adrenoceptor agonists are associated with the potential for side-effect liabilities including hypertension, stroke, insomnia and nervousness. We propose than a selective alpha 2-adrenoceptor agonist, by acting preferentially on nasal venous capacitance vessels, will elicit decongestion with a reduced side-effect liability. In the present study, we evaluated the effects of the selective alpha 2-adrenoceptor agonist BHT-920 in a real-time tissue contractility assay using isolated pig nasal explants and in an in vivo cat model of congestion. The vasoconstrictor and decongestant effects of BHT-920 were compared to the non-selective alpha-adrenoceptor agonist epinephrine and the standard decongestant oxymetazoline. Our results showed that the alpha 2-adrenoceptor agonist BHT-920 preferentially contracts venous sinusoids confirming previous observations [Corboz MR, Varty LM, Rivelli MA, Mutter JC, Mingo G, McLeod R, et al. Effects of an alpha 2-adrenoceptor agonist in nasal mucosa. Arch Physiol Biochem 2003;11: 335-6, Corboz MR, Rivelli MA, Varty LM, Mutter J, Cartwright M, Rizzo CA, et al. Pharmacological characterization of postjunctional alpha-adrenoceptor in human nasal mucosa. Am J Rhinol 2005;19: 495-502] and displays decongestion without affecting blood pressure. Therefore, an alpha 2-adrenoceptor agonist, by causing constriction in the capacitance vessels of nasal mucosa, can produce nasal decongestion without the effects on blood pressure observed with the standard selective alpha 1-adrenoceptor and non-selective alpha-adrenoceptor sympathomimetic decongestants.

Techniques d’étude pharmacologique et clinique de l’obstruction nasale : application à la xylométazoline

Nasal obstruction, a prominent feature of rhinitis, may be quantified in humans by haemodynamic techniques (measuring local blood flux), static methods (measuring the geometry of nasal cavities) and dynamic methods (assessing the patency of nasal airways through the measure of resistance to air flow). These methods demonstrated the nasal decongestant activity of xylometazoline in healthy volunteers and rhinitis patients. Controlled double-blind studies established the clinical efficacy of xylometazoline in infectious and allergic (seasonal and perennial) rhinitis versus placebo and in comparison with various reference substances. The effects on nasal epithelium ciliary activity which are observed in vitro are modest and even less pronounced in vivo owing to dilution in situ and protective physiological processes.

Immediate effect of benzalkonium chloride in decongestant nasal spray on the human nasal mucosal temperature

Benzalkonium chloride is a preservative commonly used in nasal decongestant sprays. It has been suggested that benzalkonium chloride may be harmful to the nasal mucosa. Decongestion with the vasoconstrictor xylometazoline containing benzalkonium chloride has been shown to cause a significant reduction of the nasal mucosal temperature. The purpose of the present study was to determine the short-term influence of xylometazoline nasal spray with and without benzalkonium chloride on the nasal mucosal temperature. Healthy volunteers (30) were included in the study. Fifteen volunteers received xylometazoline nasal spray (1.0 mg/mL) containing benzalkonium chloride (0.1 mg/mL) and 15 age-matched subjects, received xylometazoline nasal spray without benzalkonium chloride. Using a miniaturized thermocouple the septal mucosal temperature was continuously measured at defined intranasal detection sites before and after application of the nasal spray. The mucosal temperature values did not significantly differ between the group receiving xylometazoline containing benzalkonium chloride and the group receiving xylometazoline spray without benzalkonium chloride before and after decongestion (P > 0.05). In both study groups septal mucosal temperatures significantly decreased after decongestion (P < 0.05) because of a reduction of the nasal mucosal blood flow following vasoconstriction. This study indicates that benzalkonium chloride itself does not seem to influence nasal blood flow and nasal mucosal temperature in topical nasal decongestants.

Phenylpropanolamine constricts mouse and human blood vessels by preferentially activating alpha2-adrenoceptors

Phenylpropanolamine (dl-norephedrine) was one of the most widely used therapeutic agents to act on the sympathetic nervous system. Because of concerns regarding incidents of stroke, its use as a nasal decongestant was discontinued. Although considered an alpha1-adrenergic agonist, the vascular adrenergic pharmacology of phenylpropanolamine was not fully characterized. Unlike most other circulations, the vasculature of the nasal mucosa is highly enriched with constrictor alpha2-adrenoceptors. Therefore, experiments were performed to determine whether phenylpropanolamine activates vascular alpha2-adrenoceptors. Mouse tail and mesenteric small arteries and human small dermal veins were isolated and analyzed in a perfusion myograph. The selective alpha1-adrenergic agonist phenylephrine caused constriction of tail and mesenteric arteries and human veins. The selective alpha2-adrenergic agonist UK14,304 [5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine] caused constriction in tail arteries and in human veins, but not mesenteric arteries. The lack of constriction to UK14,304 was also observed in endothelium-denuded mesenteric arteries. Phenylpropanolamine constricted both types of artery but was 62-fold more potent in tail arteries. In mesenteric arteries, constriction to phenylpropanolamine was not affected by the selective alpha2-adrenergic antagonist, rauwolscine (10(-7) M) but was abolished by the selective alpha1-adrenergic antagonist, prazosin (3 x 10(-7) M). In contrast, constriction to phenylpropanolamine in tail arteries and in human veins was inhibited by rauwolscine but not prazosin. Therefore, phenylpropanolamine is a preferential alpha2-adrenergic agonist. At low concentrations, it constricts blood vessels that express functional alpha2-adrenoceptors, whereas at much higher concentrations, phenylpropanolamine also activates vascular alpha1-adrenoceptors. This action likely contributed to phenylpropanolamine's therapeutic activity, namely constriction of the nasal vasculature.

Pharmacological characterization of alpha 2-adrenoceptor-mediated responses in pig nasal mucosa

1. Pig nasal mucosal strips were incubated with alpha-adrenoceptor antagonists followed by alpha2-adrenoceptor agonist concentration-response curves. 2. Contractions elicited by the alpha2-adrenoceptor agonists BHT-920 (pD2 = 6.16 +/- 0.07), UK 14,304 (pD2 = 6.89 +/- 0.13) and PGE-6201204 (pD2 = 7.12 +/- 0.21) were blocked by the alpha2-adrenoceptor antagonist yohimbine (0.1 microm). In contrast, the alpha1-adrenoceptor antagonist prazosin (0.03 microm) had no effect on the BHT-920-, UK 14,304- and PGE-6201204-induced contractions, but blocked the contractile response to the alpha(1)-adrenoceptor agonist phenylephrine (pD2 = 5.38 +/- 0.04) and the mixed alpha1- and alpha2-adrenoceptor agonist oxymetazoline (pD(2) = 6.30 +/- 0.22). 3. The alpha2-adrenoceptor antagonist yohimbine (0.01-0.1 microm, pA2 = 8.04), alpha2B/C-adrenoceptor antagonist ARC 239 (10 microm, pK(b) = 6.33 +/- 0.21), alpha2A/C-adrenoceptor antagonist WB 4101 (0.3 microm, pK(b) = 8.01 +/- 0.24), alpha2A-adrenoceptor antagonists BRL44408 (0.1 microm, pK(b) = 6.82 +/- 0.34) and RX 821002 (0.1 microm, pKb = 8.31 +/- 0.35), alpha2C-adrenoceptor antagonists spiroxatrine (1 microm, pKb = 7.32 +/- 0.32), rauwolscine (0.1 microm, pKb = 8.16 +/- 0.14) and HV 723 (0.3 microm, pKb = 7.68 +/- 0.14) inhibited BHT-920-induced contractions in pig nasal mucosa. 4. The present antagonist potencies showed correlations with binding affinity estimates (pKi) obtained for these antagonists at the human recombinant alpha2A- and alpha2C-adrenoceptors (r = 0.78 and 0.83, respectively) and with binding affinity estimates (pKd) obtained in pig native alpha2A- and alpha2C-monoreceptor assays (r = 0.85 and 0.78, respectively). No correlation was observed for the alpha2B-subtype. 5. In conclusion, contractile responses to phenylephrine, BHT-920, UK 14,304, PGE-6201204 and oxymetazoline indicate that alpha1- and alpha2-adrenoceptors are present and mediate vasoconstriction in pig nasal mucosa. Furthermore, correlation analysis comparing antagonist potency in pig nasal mucosa with affinities for human recombinant alpha2-adrenoceptors and native pig alpha2-adrenoceptors suggest that alpha2A- and alpha2C-adrenoceptor subtypes constrict pig nasal mucosa vasculature.

Adrenergic mechanisms in canine nasal venous systems

1 We investigated the adrenergic mechanisms of the two venous systems that drain the nasal mucosa, thereby their exact role in eliciting nasal decongestion. The action of endogenously released noradrenaline and exogenous adrenergic agonists on different segments of the nasal venous systems, i.e. collecting (LCV, SCV) and outflow (SPV) veins of posterior venous system, collecting (ACV) and outflow (DNV) veins of anterior venous system and venous sinusoids of the septal mucosa (SM), were studied. In vitro isometric tension of the vascular segments was measured. 2 Transmural nerve stimulation (TNS) produced constriction in ACV, DNV and SM, primary constriction followed by secondary dilatation in LCV and SCV and dilatation in SPV. Tetrodotoxin (10(-6) M) abolished all responses. Phentolamine (10(-6) M), prazosin (10(-6) M) and rauwolscine (10(-7) M) inhibited the constriction in all venous vessels. Propranolol (10(-6) M), atenolol (10(-6) M) and ICI 118,551 (10(-6) M) inhibited the relaxation in SPV but not in LCV and SCV. Phenylephrine and clonidine constricted whereas dobutamine and terbutaline relaxed all venous vessels dose-dependently. 3 These results indicate alpha(1)-, alpha(2)-, beta(1)- and beta(2)-adrenoceptors are present in both venous systems. TNS causes constriction of anterior venous system, venous sinusoids and posterior collecting veins primarily via postjunctional alpha(2)-adrenoceptors but relaxation of posterior outflow vein equally via postjunctional beta(1)- and beta(2)-adrenoceptors. The combined action of the two adrenergic mechanisms can reduce nasal airway resistance in vivo by decreasing vascular capacitance and enhancing venous drainage via the posterior venous system.

Detection of particles within the nasal airways before and after nasal decongestion

Cleansing of the air is one of the most important functions of the nose. The aim of this investigation was to determine the influence of decongestion of the nasal mucosa with xylometazoline on the intranasal particle deposition at different sites of the nasal cavity. During respiration of an aerosol of starch particles, the non-deposited particles in the air were laseroptically detected in 10 healthy volunteers by a transnasally placed suction probe at different locations within the nasal cavity. The anterior nasal segment was the main area of intranasal particle deposition before and after decongestion of the nasal mucosa. Particle deposition after nasal decongestion was not significantly different from the values before application of xylometazoline. Decongestion of the nasal mucosa and increase in nasal cavity diameter seems not to influence particle deposition of inhaled and exhaled air within a short period after onset of the maximal decongestive effect of xylometazoline.

Sympathetic control of nasal blood flow in the rat mediated by alpha(1)-adrenoceptors

Experiments were undertaken, using laser-Doppler flowmetry, to determine the nature of adrenoceptors mediating sympathetic nerve evoked nasal vasoconstrictor responses in anesthetized rats. Presence of sympathetic tone was confirmed by a large (330%) increase of nasal blood flow following section of the ipsilateral preganglionic cervical sympathetic nerve. Electrical nerve stimulation produced reproducible, frequency-related nasal vasoconstrictor responses with near maximal response, observed at less than 10 Hz. Evoked nasal vasoconstrictor responses were largely blocked with intravenous treatment with the non-selective alpha-adrenoceptor antagonists, phentolamine (5 mg kg(-1)) and phenoxybenzamine (2 mg kg(-1)), as well as with the selective alpha(1)-adrenoceptor antagonist, prazosin (300 microg kg(-1)). alpha(2)-Adrenoceptor antagonism with rauwolscine (500 microg kg(-1)) potentiated neurally evoked nasal vasoconstriction. Neither atropine (1 mg kg(-1)) nor propranolol (1 mg kg(-1)) altered the evoked responses. Rats with intact cervical sympathetic nerves responded to rauwolscine with a modest constriction. Subsequent prazosin administration produced an increase of nasal blood flow of approximately 275%. These results suggest that the nasal vasculature of the rat is under intense sympathetic tone and that the resulting neurogenic vasoconstriction is mediated exclusively by activation of alpha(1)-adrenoceptors.

Beta-adrenergic mechanisms in the nasal mucosa vascular bed

In thiopentone-anesthetized mature pigs (n = 7), local intra-arterial infusion of the beta 2-adrenoceptor agonists terbutaline and salbutamol and the beta 3-agonist BRL 37344 induced dose-dependent increases in nasal arterial blood flow (BF) and volume of the nasal mucosa (reflecting capacitance vessel function). Increases were also found in the laser Doppler flowmeter signal, reflecting superficial mucosal BF. In contrast to terbutaline and salbutamol, BRL 37344 showed marked effects on volume. Pretreatment with the beta-adrenoceptor blocker propranolol significantly reduced the vasodilatory effects of terbutaline and salbutamol, whereas the BF increase evoked by BRL 37344 was not affected. Exogenous noradrenaline (NA) induced in vitro dose-dependent contractions of human nasal mucosa biopsies obtained from patients with non-allergic chronic rhinitis (n = 21) or non-allergic nasal polyposis (NANP, n = 16). On a molar basis, the contractile effect of NA was significantly greater in nasal mucosa samples without histological abnormalities when compared to biopsies with abundant inflammatory cells and edema within the submucosa. In the presence of propranolol, the vasoconstrictor effect of NA was significantly enhanced in biopsies with abundant inflammatory cells obtained from patients with NANP (P < 0.01). This observation suggests the possible occurrence of a beta 2 hyper-reactivity in the nasal mucosa of patients with NANP. After precontraction in a Krebs-Ringer solution with 50 nM K+, all nasal biopsies studied showed dose-dependent relaxation to terbutaline, salbutamol and BRL 37344. This relaxant effect was markedly reduced after pretreatment with propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of oxymetazoline on nasal and sinus mucosal blood flow in the rabbit as measured with laser-Doppler flowmetry

The effect of topical oxymetazoline hydrochloride on the blood flow of the nasal and sinus mucosa of the rabbit was measured by laser-Doppler flowmetry. Oxymetazoline, the active component in clinically used nose drops, induced a dose-dependent decrease of the nasal mucosal blood flow. This effect has previously been shown in humans and suggests the presence of alpha 2-adrenoceptors in the nasal mucosa of the rabbit. Doses of oxymetazoline used clinically in humans induced a 50% reduction of blood flow in rabbits. Rhythmic variations in blood flow were seen in 30% of the rabbits after administration of oxymetazoline. Additionally, oxymetazoline induced a dose-dependent decrease of the mucosal blood flow in the maxillary sinus when the drug was applied in the nose. A vasoconstricting effect of oxymetazoline on the arteries penetrating the maxillary sinus ostium is a possible explanation. This can have positive as well as negative consequences on acute sinus infections.

Increased pressure in venous sinusoids during decongestion of rat nasal mucosa induced by adrenergic agonists

The haemodynamic effects of sympathetic agonists causing decongestion of the nasal mucosa have been investigated in rats. Access to mucosa was obtained from the dorsal side through a small cavity drilled in the nasal bone. The pressures in the venous sinusoids and in the interstitial fluid of nasal mucosa were recorded by micropuncture technique. The local red cell flux (LDF) was monitored by laser Doppler flowmetry, and the blood volume in the mucosa was measured by radio-labelled erythrocytes and albumin. In control rats the tissue blood volume was 0.25 +/- 0.03 g (g wet wt)-1. The interstitial fluid pressure (IFP) was 2.4 +/- 0.6 mmHg and the average blood pressure in venous sinusoids (Ps) was 12.8 +/- 2.7 mmHg. After topical application of noradrenaline (NA) the local blood volume was reduced to 0.12 +/- 0.03 g g-1. Ps was increased to 18.0 +/- 4.0 mmHg, whereas IFP was maintained and LDF was reduced to 40.4% of control, indicating a greater rise in post than in presinusoid vascular resistance. Blocking of both alpha 1 and alpha 2-receptors by phentolamine caused a rise in mucosa blood volume and in LDF by 16 and 20% of control, respectively. Ps increased significantly to 15.2 +/- 3.3 mmHg. Specific stimulation or blocking of alpha 1-receptors by phenylephrine or prazosin induced similar or slightly smaller vascular responses than NA or phentolamine. The effects of the specific alpha 2-agonist (clonidine) or antagonist (yohimbine) on rat mucosa were small, indicating a domination of the alpha 1-receptors. Thus, application of NA caused a rise in blood pressure in the venous sinusoids of nasal mucosa. As LDF fell simultaneously, the reduced blood volume must be due to an increased tone in the muscular wall of venous sinusoids.

Functional disturbances of the autonomic nerve in nasal hyperreactivity: an up-date review

During the 1980s, our view of airway hypersensitivity was altered significantly. Advances in biochemical techniques revealed involvement of several nonspecific events in nasal hyperreactivity: Autonomic dysfunction involving primary and/or secondary receptor disorders, epithelial damage by cytotoxic proteins in eosinophil, which is stimulated by inflammatory mediators, and an axonal reflex of sensory C fibers. Since 1983, we have neurobiochemically investigated the autonomic nerve dysfunction in the nasal mucosa of patients with nasal allergy and guinea pigs with experimentally-induced nasal hypersensitivity. We propose the following mechanisms as potential contributors to the disturbance of the beta receptor function in airway hyperreactivity: i) Down-regulation caused by excess endogenous norepinephrine stimulation, ii) down-regulation and uncoupling to adenylate cyclase, produced by the inflammatory mediator-induced activation of protein kinase C, iii) the action of beta receptor inhibitory factor, presumably anti beta receptor autoantibodies, and iv) dysfunction of beta receptor kinase, which is known to cause short-term desensitization of beta receptors after exposure to beta agonists. This review provides the anatomical and neurobiochemical background for the autonomic regulation and dysfunction in the nose. We also introduce our series of experiments and the above updated hypotheses of how functional disturbances of the autonomic nerve in the nasal mucosa may occur.

Vascular control of the pig nasal mucosa: distribution and effect of somatostatin in relation to noradrenaline and neuropeptide Y

By means of immunohistochemistry and radioimmunoassay (RIA), we have investigated the possible occurrence of somatostatin (SOM)-like immunoreactivity (-LI) in the autonomic innervation of the pig nasal mucosa. SOM-immunoreactive (-IR) fibres were present around nasal arteries, arterioles and venous sinusoids. Double-labelling experiments revealed that SOM-LI was co-localized with the noradrenaline (NA) markers tyrosine hydroxylase and dopamine-beta-hydroxylase as well as with neuropeptide Y (NPY) in a subpopulation of neurons in the superior cervical sympathetic ganglion and in perivascular nerve terminals. Furthermore, SOM-LI was also present in perivascular fibres containing vasoactive intestinal polypeptide (VIP) and NPY of presumably parasympathetic origin. The parasympathetic fibres that were associated with glands contained peptide histidine isoleucine (PHI), VIP and NPY but not SOM, suggesting that in the nasal mucosa SOM-IR is restricted to perivascular nerves. As revealed by RIA, the content of SOM-LI in biopsies of both nasal mucosa and superior cervical sympathetic ganglion was about 12 pmol/g and the reverse phase HPLC characterisation of SOM-LI shown two separate peaks for SOM-28 and SOM-14. In thiopentone anaesthetized pigs (n = 10), local intra-arterial (i.a.) infusion of SOM (1-14) induced dose-dependent, long lasting and parallel reduction of the nasal arterial blood flow, the volume of the nasal mucosa (reflecting capacitance vessel function) and decrease of the laser Doppler flowmeter signal (reflecting superficial nasal mucosal blood flow). These functional responses were not modified after pretreatment with the alpha-adrenoceptor antagonist phenoxybenzamine (1 mg kg-1 i.a.) whereas the effects of NA were almost abolished. SOM (6.10(-6) mol, i.a.) did not influence the nasal vascular responses to single impulse stimulation of the nasal sympathetic nerve supply providing no evidence for prejunctional activity in spite of clear-cut vascular effects. It is concluded that SOM-LI is co-localized with NA and NPY in sympathetic nerves and with VIP/NPY in parasympathetic perivascular nerves of the pig nasal mucosa. Since SOM evokes vasoconstriction via non-adrenergic mechanisms, this peptide should also be considered when discussing mediator candidates for the neural regulation of the nasal vascular bed.

Methylene blue attenuates vasodilation and enhances vasoconstriction in response to endothelin-1 in the pig nasal mucosa

In thiopentone anaesthetized pigs (n = 10), simultaneous recordings of the vasomotor response to local intra-arterial infusion of endothelin-1 and -3 were performed in three different vascular compartments of the nasal mucosa. Sphenopalatine artery blood flow (reflecting nasal blood flow), nasal cavity volume (representing blood content in capacitance vessels) and laser Doppler flowmeter signal (reflecting superficial mucosal blood flow) increased in response to low doses (4 x 10(-9) to 4 x 10(-8) moles) of endothelin-1. In contrast, marked vasoconstriction (up to 50% of arterial blood flow reduction) occurred upon higher doses (4 x 10(-7) to 4 x 10(-6) moles). Endothelin-3 (4 x 10(-9) to 4 x 10(-6) moles) evoked at the highest dose a long-lasting increase of systemic arterial blood pressure resulting in a 22 +/- 4% increase in nasal vascular resistance. After local intra-arterial pretreatment with methylene blue (4 x 10(-4) mol), the vasodilatory responses to low doses of endothelin-1 were abolished for the three vascular parameters studied, whereas the vasoconstrictor responses in resistance and capacitance vessels evoked by higher doses of endothelin-1 were increased. In contrast, the laser Doppler flowmeter signal reduction in response to endothelin-1 was markedly attenuated. The vasodilatatory effect of substance P was abolished after methylene blue probably due to interference with effects of endothelium dependent relaxing factor (EDRF). These observations suggest that in the pig nasal mucosa in vivo, exogenous endothelin-1 induces a dose-dependent reduction of blood flow in resistance and capacitance vessels and in superficial mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of calcitonin gene-related peptide in the pig nasal mucosa by antidromic nerve stimulation and capsaicin

The overflow of calcitonin gene-related peptide like-immunoreactivity (CGRP-LI) in the nasal venous effluent upon antidromic stimulation of the maxillary division of the trigeminal nerve with 6.9 Hz for 3 min or upon capsaicin (0.3 mumol bolus injection) were analysed in the nasal mucosa of sympathectomized pentobarbital anaesthetized pigs. The overflow of CGRP-LI upon antidromic stimulation displayed a slower appearance in the venous effluent than the overflow upon bolus injection of capsaicin. The vascular effects as revealed by the arterial blood flow, the venous blood flow, the blood volume of the nasal mucosa, i.e., the filling of the capacitance vessels and the superficial mucosal blood flow as revealed by the laser-Doppler signal were also studied. Antidromic stimulation of the trigeminal nerve as well as capsaicin bolus injection induced a marked vasodilation which was parallel to the overflow of CGRP. However, capsaicin bolus injection also resulted in a marked increase in the mean arterial blood pressure which may be due to reflex activation of sympathetic fibers. In conclusion, we have demonstrated that chemical stimulation with capsaicin as well as antidromic stimulation of nasal sensory nerves in sympathectomized animals induces both vasodilation and overflow of CGRP-LI in vivo. This indicates that CGRP may contribute to the sensory regulation of the microcirculation in the nasal mucosa.

A comparison of laser Doppler flowmetry with the radiolabelled microsphere reference flow technique to measure tracheal blood flow in dogs

Measurements of tracheal wall blood flow were made in anaesthetized, ventilated dogs during resting ventilatory conditions, during application of positive end-expiratory pressure (PEEP) and during eucapnic hyperventilation of dry air, using laser Doppler flowmetry and the radiolabelled microsphere reference flow technique. Six regions of the trachea were studied in each dog, and the average laser Doppler flowmetry measurement derived from 12 sites within each region was compared with the reference flow measurement, obtained using 15 microns diameter microspheres labelled with 113Sn, 103Ru, 141Ce or 151Gd. Under each set of ventilatory conditions, there was a weak, but significant, correlation between laser Doppler flowmetry and reference flow values (baseline r = 0.44, hyperventilation r = 0.44, and PEEP r = 0.74). Average laser-Doppler flowmetry and reference flow values showed a similar reduction from baseline during application of PEEP. The mean (SD) change from baseline, expressed as a percentage, was -63 (15)% for laser-Doppler flowmetry values, and -63 (21)% for reference flow values. However, there was no correlation between the magnitude of change measured in individual regions using the two techniques. During hyperventilation, laser Doppler flowmetry measurements showed variable changes from baseline, and the mean change was -12 (45)%, which was not significantly different from zero. Reference flow values increased during hyperventilation, the mean change being 87 (77)%. The results indicate that laser Doppler flowmetry and reference flow measurements of airway wall blood flow are not directly comparable.

Adrenergic and neuropeptide Y supersensitivity in denervated nasal mucosa vasculature of the pig

The effects of sympathetic denervation for 2 weeks on vasoconstrictor reactivity to alpha-adrenoceptor agonists, neuropeptide Y (NPY) and alpha,beta-methylene adenosine triphosphate (mATP) were investigated in different vascular compartments of the nasal mucosa of pentobarbital-anesthetized pigs. Supersensitivity to the vasoconstrictor actions of noradrenaline (NA) was observed in the function of both resistance vessels (as revealed by a reduction in arterial blood flow) and capacitance vessels (reflected by a reduction in nasal mucosal volume). The NA supersensitivity was, to a large extent, of prejunctional type since inhibition of neuronal uptake by desipramine also markedly enhanced the NA response. Whereas the reduction in arterial blood flow and in mucosal volume induced by the alpha 1-agonist, phenylephrine, was not changed by denervation, the effects of the alpha 2-agonists UK 14.304 and oxymetazoline were enhanced and/or prolonged. Furthermore, the reduction in blood flow and volume induced by NPY was enhanced in both amplitude and duration. The effects of mATP on the amplitude of the volume response and the duration of the blood flow and volume changes were increased. The maximal reduction in superficial blood flow was larger, as revealed by the laser Doppler flowmetry signal, when NPY or adrenoceptor agonists were given to denervated animals. It is concluded that sympathetic denervation is associated with increased sensitivity and prolonged responses to a variety of vasoconstrictor agents in the pig nasal mucosa in vivo. However, alpha 2-adrenoceptor, NPY and mATP mechanisms seem to be influenced more by denervation than by alpha 1-adrenoceptor sensitivity.