THE ADRENERGIC INNERVATION OF THE NASAL MUCOSA OF CERTAIN MAMMALS

Pharmacological Characterization of Postjunctional α-Adrenoceptors in Human Nasal Mucosa

Background

Functional α1- and α2-adrenoreceptor subtype pharmacology was characterized in an in vitro human nasal mucosa contractile bioassay.

Methods

Nasal mucosa was obtained from 49 donor patients and mucosal strips were placed in chambers filled with Krebs–Ringer solution and attached to isometric force transducers.

Results

Nonselective α-adrenoreceptor agonists epinephrine, norepinephrine, and oxymetazoline produced concentration-dependent contractions of isolated human nasal mucosa (pD2= 5.2, 4.9, and 6.5, respectively). The α2-adrenoreceptor agonist BHT-920 (10 μM)–induced contractions were blocked by yohimbine (0.01–1 μM) and prazosin (0.01–1 μM) inhibited the contractile response to the α1-adrenoreceptor agonist phenylephrine (10 μM). Histological analysis showed that phenylephrine and BHT-920 differentially contracted the arteries and veins of human nasal mucosa, respectively.

Conclusion

Our results indicate that functional α1- and α2-adrenoceptors are present and functional in human nasal mucosa. The a 2-adrenoceptors display a predominant role in contracting the veins and the α1-adrenoceptors appear to preferentially constrict the human nasal arteries.

Imidazoline use in sinonasal surgery

The nasal mucosa is very vascular, receiving more blood flow per cubic centimeter of tissue than does muscle, brain or liver (Drettner and Aust, 1974; [1]). This vascularity can present a major problem during sinus surgery. Surgeons routinely use topical vasoconstrictors in endoscopic sinus surgery however, the optimal regimen is not clear. Imidazoline nasal sprays are often used up to 1hour before sinonasal surgery to aid in intraoperative vasoconstriction. After the induction of anaesthesia, epinephrine-based topical and submucosal preparations are subsequently administered to further enhance vasoconstriction. Imidazolines are non-selective, partial alpha adrenoceptor agonists with a higher affinity, yet lower potency, for alpha adrenoceptors when compared to epinephrine. It is hypothesized that imidazolines block the action of epinephrine on the alpha adrenoceptors of the nasal mucosa resulting in less vasoconstriction, and a poorer intra-operative field, when compared to the use of epinephrine alone. This paper hypothesizes that preoperative imidazoline administration may adversely affect optimal intra-operative vasoconstriction.

Are the precapillary sphincters and metarterioles universal components of the microcirculation? An historical review

The microcirculation is a major topic in current physiology textbooks and is frequently explained with schematics including the precapillary sphincters and metarterioles. We re-evaluated the validity and applicability of the concepts precapillary sphincters and metarterioles by reviewing the historical context in which they were developed in physiology textbooks. The studies by Zweifach up until the 1950s revealed the unique features of the mesenteric microcirculation, illustrated with impressive schematics of the microcirculation with metarterioles and precapillary sphincters. Fulton, Guyton and other authors introduced or mimicked these schematics in their physiology textbooks as representative of the microcirculation in general. However, morphological and physiological studies have revealed that the microcirculation in the other organs and tissues contains no metarterioles or precapillary sphincters. The metarterioles and precapillary sphincters were not universal components of the microcirculation in general, but unique features of the mesenteric microcirculation.

Surgery of the turbinates and "empty nose" syndrome

Surgical therapy of the inferior and/or middle turbinate is indicated when conservative treatment options have failed. The desired goal is a reduction of the soft tissue volume of the turbinates regarding the individual anatomic findings, whilst simultaneously conserving as much mucosa as possible. As the turbinates serve as a functional entity within the nose, they ensure climatisation, humidification and cleaning of the inhaled air. Thus free nasal breathing means a decent quality of life, as well.Regarding the multitude of different surgical techniques, we confirm that no ideal standard technique for turbinate reduction has been developed so far. Moreover, there is a lack of prospective and comparable long-term studies, which makes it difficult to recommend evidence-based surgical techniques. However, the anterior turbinoplasty seems to fulfil the preconditions of limited tissue reduction and mucosa-preservation, and therefore it is the method of choice today.Radical resection of the turbinates may lead to severe functional disturbances developing a secondary atrophic rhinitis. The "empty nose" syndrome is a specific entity within the secondary atrophic rhinitis where intranasal changes in airflow result in disturbed climatisation and also interfere with pulmonary function. Results deriving from an actual in vivo study of climatisation and airflow in "empty nose" patients are presented.

Numerical simulation and nasal air-conditioning

Heating and humidification of the respiratory air are the main functions of the nasal airways in addition to cleansing and olfaction. Optimal nasal air conditioning is mandatory for an ideal pulmonary gas exchange in order to avoid desiccation and adhesion of the alveolar capillary bed. The complex three-dimensional anatomical structure of the nose makes it impossible to perform detailed in vivo studies on intranasal heating and humidification within the entire nasal airways applying various technical set-ups. The main problem of in vivo temperature and humidity measurements is a poor spatial and time resolution. Therefore, in vivo measurements are feasible only to a restricted extent, solely providing single temperature values as the complete nose is not entirely accessible. Therefore, data on the overall performance of the nose are only based on one single measurement within each nasal segment. In vivo measurements within the entire nose are not feasible. These serious technical issues concerning in vivo measurements led to a large number of numerical simulation projects in the last few years providing novel information about the complex functions of the nasal airways. In general, numerical simulations merely calculate predictions in a computational model, e.g. a realistic nose model, depending on the setting of the boundary conditions. Therefore, numerical simulations achieve only approximations of a possible real situation. The aim of this review is the synopsis of the technical expertise on the field of in vivo nasal air conditioning, the novel information of numerical simulations and the current state of knowledge on the influence of nasal and sinus surgery on nasal air conditioning.

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.

[Neural control of the respiratory nasal mucosa]

Respiratory nasal mucosa fulfils the function of pretreating the inspired air. The periodic nasal cycle and pathologic functional disturbances of the endonasal tissue influence the nasal passages. The secretion of the seromucous glands and extravasation from the blood vessels are essential for mucocilliary transport. These physiological mechanisms are partially controlled by neural regulation. Besides classic neurotransmitter neuropeptides such as VIP, CGRP, SP and NPY, nitric oxide also shares this role. A network of sensory, sympathetic and parasympathetic nerve fibres protects the respiratory mucous membranes from external and internal irritation. In addition, blood vessels and glands are influenced by endothelial and humoral factors. For the different types of rhinitis, sensory neuropeptides and inflammatory mediators take part in the pathomechanisms and can lead to a so called neurogenic inflammation of the nasal mucosa.

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.

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.

Nasal airflow in health and disease

This review examines our present understanding of the physiology, pathophysiology and pharmacology of nasal airflow. The main aim of the review is to discuss the basic scientific and clinical knowledge that is essential for a proper understanding of the usefulness of measurements of nasal airflow in the clinical practice of rhinology. The review concludes with a discussion of the measurement of nasal airflow to assess the efficacy of surgery in the treatment of nasal obstruction. Areas covered by the review include: influence of nasal blood vessels on nasal airflow; nasal valve and control of nasal airflow; autonomic control of nasal airflow; normal nasal airflow; nasal cycle; central control of nasal airflow; effect of changes in posture on nasal airflow; effect of exercise on nasal airflow; effect of hyperventilation and rebreathing on nasal airflow; nasal airflow in animals; cerebral effects of nasal airflow; sensation of nasal airflow; sympathomimetics and sympatholytics; histamine and antihistamines; bradykinin; and corticosteroids.

Basic innervation pattern and distribution of classic autonomic neurotransmitters in human nasal mucosal vasculature

The neural control of human nasal vasculature is still not completely understood. This study was performed to demonstrate the innervation pattern of the different vessel types and to distinguish between nor-adrenergic and cholinergic structures. General innervation was demonstrated using antibodies to neuron-specific enolase and S-100 protein. Autonomic structures were shown by using antibodies to tyrosine hydroxylase and choline acetyltransferase (ChAT). In addition, choline acetyltransferase (AChe) histochemistry was performed. Nasal vasculature is controlled by a dense innervation that increases with the thickness of the tunica media. While all larger vessels show a mixed autonomic innervation, sympathetic structures seem to predominate in veins. These findings demonstrate that classic neurotransmitters play a major role in the regulation of nasal vasculature. The stronger innervation of arteries and cushion veins underlines their central position in the control of nasal air flow.

Changes in the amplitude of the nasal cycle associated with symptoms of acute upper respiratory tract infection

Nasal airflow is normally asymmetrical and subject to spontaneous reciprocal changes which are often referred to as the 'nasal cycle'. The nature of these spontaneous changes in nasal resistance is poorly understood and little information is available about how they are affected by nasal disease. In order to understand the changes in nasal resistance in health and disease it is important to record unilateral resistance rather than express results as total nasal resistance. Unilateral resistance is subject to continuous reciprocal changes and therefore new measurements were developed in this study in order to quantify the nasal resistance of each nasal passage. Twelve human subjects (age 19-38) with symptoms of acute respiratory tract infection (URTI) were recruited for the study which involved serial measurements of unilateral nasal airway resistance using the technique of posterior rhinomanometry over a period of six hours. Measurements were made on one day when subjects had symptoms of URTI and then repeated 6-8 weeks later when subjects were healthy. The results of this study show that all of the subjects exhibited spontaneous reciprocal changes in nasal airway resistance on both study days but that there was a significant increase in the amplitude of the changes in resistance when the subjects had symptoms of URTI with one nasal passage often becoming severely congested. In order to quantify the amplitude of the reciprocal changes in nasal resistance two new measures were used. The minimum and maximum nasal airway resistance recorded for each nasal passage during the six hour recording period (MIN NAR and MAX NAR). Mean MIN NAR with URTI was 0.4 Pa cm3s +/- 0.07 which was not significantly different from mean MIN NAR in health which was 0.36 Pa cm3s +/- 0.05 (p = 0.22, n = 20). The mean MAX NAR during URTI was 2.44 Pa cm3s +/- 0.38 and this decreased significantly to 1.36 +/- 0.17 when recorded during healthy conditions (p = 0.01, n = 20). The increased amplitude of spontaneous reciprocal changes in nasal airway resistance associated with symptoms of URTI is proposed to be due to an increased filling pressure to the nasal venous sinusoids associated with a nasal inflammatory response. A model is proposed to explain the role of the nasal sympathetic vasoconstrictor tone and nasal venous filling pressure in the control of nasal airway resistance and to help explain the periods of unilateral nasal obstruction often associated with allergic and infective rhinitis.

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)

The role of ATP in non-adrenergic sympathetic vascular control of the nasal mucosa in anaesthetized cats and dogs

1. In anaesthetized cats and dogs, local intra-arterial injection of noradrenaline and alpha, beta-methylene adenosine 5'-triphosphate (mATP) reduced both nasal arterial blood flow and nasal mucosal volume (a measure of capacitance vessel function). The responses to mATP were not modified by pretreatment with the adrenoceptor antagonists phentolamine and propranolol or the purinoceptor antagonist suramin. The vascular effects of noradrenaline were not altered by suramin, but were virtually abolished by adrenoceptor antagonists. 2. After adrenoceptor blockade, frequency-dependent reductions in nasal arterial blood flow with sympathetic nerve stimulation were reduced by 25 and 39% in cats and dogs, respectively; whereas the volume response was reduced by 56% in cats and 54% in dogs. The remaining non-adrenergic sympathetic nerve-evoked vascular responses were not influenced by suramin. 3. During desensitization to mATP induced by local intra-arterial infusion for 5 min, the remaining non-adrenergic nasal blood flow and volume responses to sympathetic nerve stimulation were reduced in the dog but not in the cat. 4. It is suggested that both adrenergic and non-adrenergic mechanisms are involved in the sympathetic control of the nasal mucosa vascular bed of both species. Since desensitization to mATP markedly reduces the remaining non-adrenergic nasal vasoconstriction evoked by sympathetic nerve stimulation in the dog, ATP is a possible sympathetic mediator in the nasal vascular bed in this species.

Origin and peptide content of nerve fibers in the nasal mucosa of rats

Injection of the retrograde neuronal tracer True blue into the anterior-lateral part of the nasal mucosa of rats labeled nerve cell bodies in the superior cervical ganglion, the sphenopalatine ganglion, the otic ganglion and the trigeminal ganglion on the ipsilateral side. In the superior cervical ganglion, the sphenopalatine ganglion and the trigeminal ganglion on the contralateral side, very few nerve cell bodies were labeled, indicating that these ganglia provide minor contributions only. The number of labeled cell bodies indicates that the superior cervical ganglion, the sphenopalatine ganglion and the trigeminal ganglion contribute most to the innervation of the nose, while the contribution from the otic ganglion is minor. Cell bodies in the superior cervical ganglion harbored noradrenaline (NA) or NA/neuropeptide Y (NPY); in the sphenopalatine ganglion vasoactive intestinal peptide (VIP) or VIP/NPY; in the otic ganglion VIP, VIP/NPY or VIP/substance P (SP) and in the trigeminal ganglion calcitonin gene-related peptide (CGRP) or CGRP/SP. The results from denervations and tracer experiments suggest that all NA-containing and the majority of NPY-containing fibers in the nasal mucosa are derived from the superior cervical ganglion (sympathetic nerve supply). VIP- and VIP/NPY-containing fibers originate from the sphenopalatine and optic ganglia (parasympathetic nerve supply). Nerve fibers containing CGRP and CGRP/SP emanate from the trigeminal ganglion (sensory nerve supply).

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.

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.

Sympathetic nerve stimulation influences mucociliary activity in the rabbit maxillary sinus

The effect of preganglionic sympathetic nerve stimulation on mucociliary activity in the rabbit maxillary sinus was investigated in vivo. Response to nerve stimulation was recorded photoelectrically and expressed as a percentage of the basal mucociliary activity prior to stimulation. Nerve stimulation (15 V, 5 ms) for 60 s at 2, 10 and 20 Hz stimulated mucociliary activity, the maximum increase being 21.1 +/- 1.3% at 20 Hz, an increase that pretreatment with the cholinergic antagonist atropine reduced to 14.5 +/- 2.4%, suggesting that part of the response involves cholinergic mechanisms. Nerve stimulation (10 Hz) of animals pretreated with the beta-adrenoceptor antagonist propranolol reversed the mucociliary response from an increase to a decrease (-10.6 +/- 1.6%), indicating the involvement of beta-receptors in the nerve-evoked increase. Pretreatment with the alpha-adrenoceptor antagonist phentolamine had no effect on response to nerve stimulation. Rabbits given a combined atropine, propranolol and phentolamine blockade manifested decreased mucociliary activity in response to nerve stimulation (-10.6 +/- 2.1%). Guanethidine pretreatment blocked the effect of nerve stimulation on mucociliary activity, including the observed decrease after combined blockade, indicating the effect to be mediated via sympathetic nerve fibres. The decrease in mucociliary activity in response to nerve stimulation after combined cholinergic-, beta-, and alpha-adrenoceptor blockade suggests the presence of a nonadrenergic, non-cholinergic inhibitory mechanism. It is possible that this effect is mediated by release of neuropeptide Y, as intraarterial injections of neuropeptide Y reduce mucociliary activity in the rabbit maxillary sinus, and as neuropeptide Y is released in the upper airways upon sympathetic nerve stimulation.

Compartment analysis of vascular effects of neuropeptides and capsaicin in the pig nasal mucosa

The vascular effects of local infusion of capsaicin, substance P (SP), calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP) were monitored in an experimental model on the pig nasal mucosa. Arterial, venous and superficial mucosal blood flow (laser-Doppler flowmetry) as well as mucosal volume, reflecting changes in capacitance vessels were studied in parallel. All substances induced concentration dependent increases in the parameters studied with the exception of the decrease in the superficial mucosal flow induced by vasoactive intestinal polypeptide. This latter finding was interpreted as a stealing phenomenon and suggests that vasoactive intestinal polypeptide mainly exerts its vasodilatory effect in the deeper glandular layers of the nasal mucosa. The vasodilatory effect of capsaicin, except the laser-Doppler signal, was markedly reduced by pretreatment with a combination of the ganglionic blocking agent chlorisondamine and atropine implying that capsaicin evokes a central reflex with a final parasympathetic pathway and release of agents like vasoactive intestinal polypeptide. The remaining capsaicin response may depend on a local effect with axon reflexes and the release of sensory neuropeptides with actions on superficial mucosal blood flow.

Methoxyphenamine inhibits basal and histamine-induced nasal congestion in anaesthetized rats

1. Nasal resistance in anaesthetized rats was assessed by measuring air overflow during ventilation of the nasal passages at constant pressure. Nasal basal resistance was reduced in a dose-dependent manner by methoxyphenamine hydrochloride (0.01-30 mg kg-1, i.v.), pseudoephedrine hydrochloride (0.03-3 mg kg-1, i.v.) and adrenaline bitartrate (0.01-3 micrograms kg-1, i.v.). Both methoxyphenamine and pseudoephedrine were less potent and less efficacious than adrenaline but caused longer-lasting responses. 2. Nasal congestion induced by histamine (0.2% nebulised solution passed into the nasal passages for 15 s) was inhibited by i.v. administration of methoxyphenamine, pseudoephedrine, adrenaline, methoxamine or tyramine: the ID50s against 0.2% histamine-induced nasal congestion were 1.16 (95% confidence limits; 0.5, 1.8) mg kg-1, 0.25 (0.19, 0.33) mg kg-1, 0.037 (0.018, 0.06) micrograms kg-1, 8.12 (6.74, 9.65) micrograms kg-1 and 30.6 (26.1, 35.8) micrograms kg-1 respectively. 3. The inhibitory effects of both methoxyphenamine and tyramine on histamine-induced nasal congestion were reduced after administration of desmethylimipramine (0.1 and 1 mg kg-1, i.v.) or prazosin (0.1 and 0.3 mg kg-1, i.v.). Similarly, the inhibitory effects of methoxamine were reduced after prazosin (0.1 and 0.3 mg kg-1). 4. These results indicate that methoxyphenamine (1 mg kg-1, i.v.) inhibits histamine-induced nasal congestion in the rat. This action, at least in part, is probably indirect being mediated by release of neuronal noradrenaline which then acts on alpha 1-adrenoceptors.

Neuropeptide Y (NPY) in human nasal mucosa

Neuropeptide Y (NPY), a potent vasoconstrictor peptide found in sympathetic neurons, was analyzed in human inferior turbinate nasal mucosal tissue. NPY content determined by radioimmunoassay was 3.13 +/- 0.79 pmol/g tissue (n = 6) in mucosa extracted with ethanol-acetic acid. NPY-immunoreactive nerves were found around small muscular arteries, arterioles, arteriovenous anastomoses, and as free fibers near arteriolar and venous vessels. They formed a plexus around the arterial vessels, and were also present between vascular smooth muscle cells. Few NPY fibers were present near glands or the epithelium. [125I]NPY binding sites were localized by autoradiography to small muscular arteries, arterioles, and a few venous sinusoids. In explant culture experiments, 4 microM NPY did not stimulate release of [3H]glucosamine-labeled glycoconjugates or lactoferrin (a product of serous cells) from nasal mucosal fragments. Degradation of NPY by a tissue homogenate was rapid (t1/2 = 13.5 +/- 2.3 min). The degradation was inhibited by thiorphan and phosphoramidon, inhibitors of neutral endopeptidase activity. NPY released from sympathetic neurons may play a role as a constrictor of arterial vessels and regulate vasomotor tone in the human nasal mucosa.

Neuropeptide Y: presence in sympathetic and parasympathetic innervation of the nasal mucosa

The occurrence of neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) in the sympathetic and parasympathetic innervation of the nasal mucosa was studied in various species including man. A dense network of NPY-immunoreactive (IR) fibres was present around arteries and arterioles in the nasal mucosa of all species studied. NPY was also located in nerves around seromucous glands in pig and guinea-pig, but not in rat, cat and man. The NPY-IR glandular innervation corresponded to about 20% of the NPY content of the nasal mucosa as revealed by remaining NPY content determined by radioimmunoassay after sympathectomy. These periglandular NPY-positive fibres had a distribution similar to the VIP-IR and PHI-IR nerves but not to the noradrenergic markers tyrosine hydroxylase (TH) or dopamine-beta-hydroxylase (DBH). The NPY nerves around glands and some perivascular fibres were not influenced by sympathectomy and probably originated in the sphenopalatine ganglion where NPY-IR and VIP-IR ganglion cells were present. The venous sinusoids were innervated by NPY-positive fibres in all species except the cat. Dense NPY and DBH-positive innervation was seen around thick-walled vessels in the pig nasal mucosa; the latter may represent arterio-venous shunts. Double-labelling experiments using TH and DBH, and surgical sympathectomy revealed that the majority of NPY-IR fibres around blood vessels were probably noradrenergic. The NPY-positive perivascular nerves that remained after sympathectomy in the pig nasal mucosa also contained VIP/PHI-IR. The major nasal blood vessels, i.e. sphenopalatine artery and vein, were also densely innervated by NPY-IR fibres of sympathetic origin. Perivascular VIP-IR fibres were present around small arteries, arterioles, venous sinusoids and arterio-venous shunt vessels of the nasal mucosa whereas major nasal vessels received only single VIP-positive nerves. The trigeminal ganglion of the species studied contained only single TH-IR or VIP-IR but no NPY-positive ganglion cells. It is concluded that NPY in the nasal mucosa is mainly present in perivascular nerves of sympathetic origin. In some species, such as pig, glandular and perivascular parasympathetic nerves, probably of VIP/PHI nature, also contain NPY.

Autonomic nervous control of nasal vasculature and airflow resistance in the anaesthetized dog

1. In pentobarbitone-anaesthetized dogs with constant-flow vascular perfusion of nasal mucosa on both sides, nasal airway resistance, vascular resistance, vascular capacitance (via changes in total venous outflow) and blood flow in the anterior and posterior venous systems were measured. 2. Electrical stimulation of the cut peripheral ends of the cervical sympathetic trunk, caudal nasal nerve, or major palatine nerve increased vascular resistance and decreased vascular capacitance and airway resistance. Propranolol and atropine had no effect on the responses while bretylium completely abolished them; phentolamine greatly lessened the vascular resistance response and partially decreased the vascular capacitance and airway responses. Hence, sympathetic stimulation causes constriction of the resistance vessels via alpha-adrenergic mechanism and constriction of capacitance vessels via alpha-adrenergic as well as some non-adrenergic and non-cholinergic mechanisms. 3. Denervation of the cervical sympathetic trunk, caudal nasal nerve and major palatine nerve decreased nasal vascular resistance and increased vascular capacitance and airway resistance, suggesting tonic sympathetic discharge to nasal mucosa via caudal nasal and major palatine nerves. 4. Electrical stimulation of the nerve of pterygoid canal decreased vascular resistance but increased vascular capacitance (in the posterior venous system) and airway resistance to low-voltage stimulation (below 10 V), and decreased vascular capacitance (in the anterior venous system) and airway resistance to high-voltage stimulation (above 10 V). Hexamethonium reversed the vascular resistance response as well as vascular capacitance and airway responses to high-voltage stimulation. Bretylium and phentolamine enhanced the vascular resistance response and reversed vascular capacitance and airway resistance responses to high-voltage stimulation. Hence, low-voltage stimulation results in parasympathetic dilatation of resistance and capacitance vessels whereas high-voltage stimulation results in parasympathetic dilatation of resistance vessels and sympathetic constriction of capacitance vessels. The parasympathetic vasodilatation was atropine resistance and the sympathetic vasoconstriction was partially via alpha-adrenergic mechanisms. 5. Denervation of the nerve of pterygoid canal did not affect vascular resistance, vascular capacitance or airway resistance suggesting negligible tonic parasympathetic and sympathetic discharges to nasal blood vessels via the nerve. 6. Simultaneous optimal stimulation of sympathetic and parasympathetic nerves resulted in vasoconstriction, especially in capacitance vessels, suggesting sympathetic predominance over parasympathetic control.

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.

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

1. The adrenoceptor mechanisms influencing the total blood flow, volume and superficial blood flow in the nasal mucosa of pigs anaesthetized with pentobarbitone have been characterized by use of various agonists and antagonists. 2. Local intra-arterial bolus injection of the selective alpha 1-agonist phenylephrine, the selective alpha 2-agonist UK 14.304, the mixed alpha 1/alpha 2-agonist oxymetazoline and the mixed alpha/beta-agonists noradrenaline (NA) and adrenaline induced dosed-related reduction of nasal arterial blood flow (BF), nasal mucosal volume (V, reflecting capacitance vessel function) and the laser Doppler flowmetry signal (LDF, reflecting superficial movement of blood cells). The rank order of alpha-agonist potency regarding BF reduction was UK 14.304 greater than oxymetazoline greater than phenylephrine = adrenaline. For the volume response the potency order was UK 14.304 greater than oxymetazoline = NA = adrenaline greater than phenylephrine while for the reduction of the LDF signal the potency was UK 14.304 = NA = adrenaline greater than oxymetazoline greater than phenylephrine. The selective beta 2-agonist terbutaline caused dose-dependent increase of BF whereas only a small augmentation of the V was obtained upon the highest dose (40 nmol) while no modification of the LDF signal was observed. 3. After pretreatment with the selective alpha 1-antagonist prazosin, the response to phenylephrine was abolished while the selective alpha 2-antagonist idazoxan attenuated the effect of UK 14.304. After pretreatment with alpha-antagonists, both NA and adrenaline caused biphasic effects with constriction followed by vasodilatation for BF, but not for V or LDF. This vasodilatation was blocked by the beta-antagonist propranolol. 4. The reduction in nasal BF and V upon sympathetic nerve stimulation was attenuated both by prazosin and idazoxan. Propranolol enhanced the remaining reduction of BF but not of V in the presence of alpha-antagonists. 5. It is concluded that alpha 2-adrenoceptor mechanisms in the pig nasal mucosa are dominating for the BF, V and LDF responses to exogenous agonists. alpha 1-Adrenoceptors also seem to be involved in the sympathetic control of BF, V and LDF. Activation of beta 2-receptors increases mainly BF and does not influence the LDF signal.

Sympathetic vascular control of the pig nasal mucosa (III): Co-release of noradrenaline and neuropeptide Y

The overflows of noradrenaline (NA) and neuropeptide Y like immunoreactivity (NPY-LI) and vascular responses upon sympathetic nerve stimulation were analysed in the nasal mucosa of pentobarbital anaesthetized pigs. In controls, a frequency-dependent increase in NA overflow was observed whereas detectable release of NPY-LI occurred only at 6.9 Hz. Parallel decreases in blood flow in the sphenopalatine artery and vein and in nasal mucosa volume (reflecting blood volume in the venous sinusoids) were observed. The laser Doppler flowmeter signal (reflecting superficial blood flow) increased upon low and decreased upon high frequency stimulation. Twenty-four hours after reserpine pretreatment and preganglionic decentralization, the NA overflow was abolished while a frequency-dependent release of NPY-LI occurred. Forty, 60 and 80% of the vasoconstrictor responses then remained upon stimulation with a single impulse, 0.59 and 6.9 Hz, respectively. Both the vasoconstriction and NPY-LI overflow, however, were subjected to fatigue upon repeated stimulation. In reserpinized animals release of NPY-LI and vasoconstrictor responses were larger upon stimulation with irregular bursts at 0.59 Hz compared to effects seen at stimulation with continuous impulses. Pre-treatment with the alpha-adrenoceptor antagonist phenoxybenzamine or the monoamine reuptake inhibitor, desipramine, enhanced NA overflow by 2-3 and 1.5 times at 0.59 and 6.9 Hz, respectively. Phenoxybenzamine significantly reduced the nerve-evoked vascular responses while the release of NPY-LI at 6.9 Hz was increased. Desipramine increased the functional responses but reduced the NPY-LI overflow. During tachyphylaxis to the vasoconstrictor effects of the stable adenosine 5'-triphosphate (ATP) analogue alpha-beta-methylene ATP (mATP) in controls, the vasoconstrictor responses as well as the NA and NPY-LI overflow to nerve stimulation were unmodified. In reserpinized animals, however, the vascular responses and the overflow of NPY-LI were reduced after mATP tachyphylaxis. These data show that both NA and NPY are released upon sympathetic nerve stimulation in the nasal mucosa in vivo and this release seems to be regulated via prejunctional alpha-adrenoceptors. The lack of effect of mATP tachyphylaxis under control conditions makes it less likely that ATP serves as a major mediator of the large nonadrenergic vasoconstrictor component.

Sympathetic vascular control of the pig nasal mucosa (2): Reserpine-resistant, non-adrenergic nervous responses in relation to neuropeptide Y and ATP

The possible occurrence of non-adrenergic mechanisms in the sympathetic vascular control of the nasal mucosa was studied in vivo using reserpine-treated pigs (1 mg kg-1, i.v., 24 h earlier) in combination with pharmacological blockade of alpha-adrenoceptors by local phenoxybenzamine (1 mg kg-1, i.a.) infusion. The nasal mucosal depletion (99%) of the content of noradrenaline (NA) in reserpinized animals was not influenced by preganglionic denervation while the depletion (44%) of neuropeptide Y (NPY) was prevented. Upon stimulation with single shocks, 25% of the arterial blood flow reduction and 47% of the nasal mucosal volume reduction (reflecting contraction of venous sinusoids) were still present after reserpine as compared with controls. In reserpinized animals, the vascular responses were slow developing and long-lasting, and about 60% remained at 0.59 Hz and more than 80% at 6.9 Hz. The vascular effects after reserpine were, however, subjected to fatigue, which may explain why phenoxybenzamine treatment still reduced the functional effects in the absence of NA. Local intra-arterial injections of NA, NPY and the metabolically stable adenosine-5'-triphosphate analogue alpha, beta-methylene ATP (mATP) caused reduction in both arterial blood flow and nasal mucosal volume. The C-terminal fragment of NPY (NPY 13-36) also induced nasal vasoconstriction although with a fivefold lower potency than NPY 1-36. Adenosine-5'-triphosphate caused a biphasic vascular effect with vasodilatatory actions at low doses and a short-lasting vasoconstriction followed by vasodilatation at very high doses (100-fold higher than the threshold response to mATP). In contrast to the response to NA, the long-lasting vascular effects of NPY and mATP were resistant to phenoxybenzamine treatment. In conclusion, although NA is likely to mediate most of the sympathetic vascular responses to low-frequency stimulation in the pig nasal mucosa, a large resistance and capacitance vessel component upon high-frequency stimulation seems to be non-adrenergic and mimicked by NPY rather than ATP.

Immunocytochemical identification of luteinizing hormone-releasing hormone-positive fibres and terminals in the olfactory system of the rat

Luteinizing hormone-releasing hormone immunoreactivity was studied in the olfactory system of the rat in combination with acetylcholinesterase histochemistry. Neuronal perikarya containing luteinizing hormone-releasing hormone lie in the medial septal nucleus, the vertical limb of the diagonal band of Broca, the olfactory tubercule and the ganglionated plexus of the terminal nerve. Labelled fibres spread in the superficial layers of the main and accessory olfactory bulbs, some encompassing the strongly acetylcholinesterase-positive atypical glomeruli. Others are observed on the medial side of the bulb, running along the terminal nerve bundles and ganglia. These fibres join the vomeronasal nerve branches and proceed distally towards the nasal cavity. In the septal submucosa, immunoreactive fibres are partly associated with the terminal nerve network. Conspicuous endings filled with luteinizing hormone-releasing hormone are observed on blood vessels of the olfactory mucosa. Such well-differentiated terminals might be the neurosecretory afferents of a new neurohemal area. Immunoreactive terminals are also observed around the excretory ducts of the anterior medial glands. We have failed to observe any labelled fibres in the olfactory and vomeronasal epithelia. The results of the present study are discussed with respect to possible functional interpretations. It is suggested that significant amounts of luteinizing hormone-releasing hormone could be released in the submucosal capillaries in spite of the scarcity of immunoreactive fibres. Similar afferents could also modulate the secretory activity of some nasal glands. Synaptic events involving the neuropeptide might occur in the olfactory bulb, particularly in atypical glomerular areas previously characterized by their high acetylcholinesterase content. Finally, no anatomical support for a chemosensory function of fibres containing luteinizing hormone-releasing hormone has been brought out by our work.

Sympathetic vascular control of the pig nasal mucosa: (I). Increased resistance and capacitance vessel responses upon stimulation with irregular bursts compared to continuous impulses

An in vivo model is described in which pentobarbital anaesthetized pigs were used to study the sympathetic nervous control of the nasal mucosal vascular bed. Changes in blood flow in the sphenopalatine artery (representing nasal blood flow) and in the volume of the nasal cavity (mainly reflecting blood content in venous sinusoids), upon electrical stimulation of the cervical sympathetic trunk, were recorded simultaneously. Single impulses (15V, 5 ms) reduced both the arterial flow and the volume of the nasal mucosa. The effects of nerve stimulation with a continuous train of impulses at 0.59, 2 and 6.9 Hz were compared with those caused by stimulation with the irregular bursting pattern, triggered by recorded human sympathetic vasoconstrictor nerve activity, with the same average frequencies. Both types of stimulation reduced nasal blood flow and volume, but the responses were significantly larger with burst stimulation at 0.59 Hz. The volume reduction was already maximal at 0.59 Hz while the blood flow response increased further higher frequencies. Local intra-arterial pretreatment with the alpha-adrenoceptor antagonist phenoxybenzamine significantly attenuated the flow and volume responses to single impulses, while clear-cut reductions in blood flow (by 40%) and volume (by 80%) remained, upon stimulation, at 6.9 Hz. Noradrenaline given intra-arterially caused a dose-dependent reduction in nasal blood flow and volume. The noradrenaline effects were blocked by phenoxybenzamine treatment. The results show that the pig nasal mucosa represents a model where both blood flow and volume changes can be studied in parallel in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of noradrenergic nerve fibers in canine nasal mucosa following selective neurectomies

In this study, we have used noradrenergic histofluorescence and selective neurectomies of the vidian, ethmoid and caudal nasal nerves to evaluate the distribution of postganglionic sympathetic fibers in the canine nasal mucosa. In conjunction with the histochemical localization of the noradrenergic fibers in the nasal mucosa after vidian neurectomy, the norepinephrine content of the mucosa was also evaluated using high-performance liquid chromatography. Unilateral neurectomy of the superior cervical ganglion (SCG) resulted in the unilateral disappearance of all noradrenergic histofluorescence in the nasal mucosa, while no morphological changes in noradrenergic fibers could be identified after neurectomy of the cervical sympathetic trunk 1 cm below the SCG. Ethmoid neurectomy caused the disappearance of noradrenergic fibers of the upper third of the nasal mucosa, while vidian neurectomy resulted in a partial loss of noradrenergic fibers in the lower two-thirds of the nasal mucosa. The loss was chiefly in the area adjacent to venous sinusoids and was responsible for 50% of the norepinephrine content of this tissue. We concluded that all the postganglionic sympathetic fibers are from the ipsilateral SCG. Some of them travel via the ethmoid nerve and innervate the upper third of the nasal mucosa. The remaining fibers travel via the vidian nerve and perhaps the vessel walls of the supplying arteries and innervate the lower two-thirds of the nasal mucosa. The vidian nerve chiefly innervates the venous sinusoids of the lower two-thirds of the nasal mucosa.

Neuropeptide Y and non-adrenergic sympathetic vascular control of the cat nasal mucosa

Neuropeptide Y (NPY) coexists with noradrenaline (NA) in a population of perivascular nerves in the cat nasal mucosa. In the present study, NPY was found to exert non-adrenergic nasal vasoconstrictor actions. Postganglionic sympathetic nerve stimulation induced a release of NPY-like immunoreactivity (LI) concomitant with vasoconstriction in the nasal mucosa. About 60 and 70% of the vasoconstrictor responses upon sympathetic stimulation at 2 and 10 Hz, respectively, remained after pretreatment with phenoxybenzamine and propranolol which abolished the effects of exogenous NA. Preganglionic denervation one week prior to the experiments did not change the vasoconstrictor response to sympathetic nerve stimulation or the NA or NPY contents of the nasal mucosa. The levels of NPY-LI in the superior cervical ganglion were however reduced. After reserpine treatment, which depleted the nasal NA content by almost 90% and the NPY content by 50%, a vasoconstrictor response to nerve stimulation was still present. After reserpine treatment combined with preganglionic denervation, nerve stimulation simultaneously induced an increased output of NPY-LI and a marked long-lasting vasoconstriction which was not influenced by phenoxybenzamine and propranolol. The reserpine-induced depletion of NA was not influenced by preganglionic denervation while the reduction in the nasal content of NPY-LI was prevented. In conclusion, NPY could be a non-adrenergic mediator of sympathetic vascular effects in cat nasal mucosa.

Retrograde axonal transport of true blue dye by the peripheral autonomic nerves in canine nasal mucosa

In this study we employed retrograde axonal transport of (E)-2,2'-vinylendi-benzofuran-5-carboxamidin-diaceturate+ ++ or true blue (TB) to study the peripheral autonomic innervation of the canine nasal mucosa. After injection of TB into the nasal mucosa, labeled neurons were found in the ipsilateral sphenopalatine ganglion (SPG) and the superior cervical ganglion (SCG). There were no labeled neurons in the middle cervical or stellate ganglia. This indicated that the origin of the postganglionic sympathetic fibers of the nasal mucosa was only from the ipsilateral SCG. When TB was injected into the nasal mucosa of dogs following a caudal or ethmoidal neurectomy, labeled neurons could still be found in the SPG and SCG. When TB was injected into the nasal mucosa of dogs following ethmoidal and vidian neurectomies or with maxillary neurectomy added, some labeled neurons could still be found in both the ipsilateral SPG and SCG. These results support the concept that another pathway--perhaps perivascular--exists for postganglionic sympathetic fibers other than the vidian and ethmoidal nerves. Labeled neurons were still observed in SPG when TB was applied to the canine nasal mucosa following neurectomy of either the ethmoidal or the caudal nasal nerve. However, retrograde labeled neurons could not be found in SPG following simultaneous neurectomies of the ethmoidal and caudal nasal nerves. These results show that the postganglionic parasympathetic fibers originating in the SPG travel along the ethmoidal and caudal nasal nerves.

Sympathetic neurogenic control of blood flow in human nasal mucosa

Nasal mucosal blood flow was investigated in patients undergoing a stellate ganglion blockade. Elimination of the sympathetic neurogenic control did not affect the resting blood flow in the mucosa, as registered with the 133Xe washout technique. This indicates that the basal sympathetic vasoconstrictor activity is low in the mucosal vessels that regulate blood flow. With laser doppler flowmetry, the normal pattern of spontaneous oscillations in blood flow was seen to be altered following stellate ganglion blockade. This suggests that vasomotion in the mucosa is partly dependent on sympathetic neurogenic activity. Furthermore, the decrease in blood flow normally induced by a peripheral cold provocation could not be elicited after the ganglion blockade, which means that the decrease is mediated by sympathetic vasoconstrictor fibres.

Characterization of alpha-adrenoceptors in the vasculature of the canine nasal mucosa

alpha-Adrenoceptors present in the vasculature of the nasal mucosa in beta-adrenoceptor blocked dogs have been characterized pharmacologically using selective alpha 1- and alpha 2-adrenoceptor agonists and antagonists. In pentobarbitone-anaesthetized dogs, intra-arterial (i.a.) administration of the selective alpha 1-agonists cirazoline and phenylephrine, the selective alpha 2-agonist UK-14,304 and the mixed alpha 1/alpha 2-agonists adrenaline, noradrenaline and oxymetazoline produced dose-related nasal vasoconstrictor responses (as measured by decreases in nasal cavity pressure). The rank order of agonist potency was adrenaline greater than oxymetazoline = UK-14,304 greater than noradrenaline greater than cirazoline greater than phenylephrine. The nasal response to cirazoline was inhibited by the selective alpha 1-adrenoceptor antagonist prazosin but not by the new, potent selective alpha 2-adrenoceptor antagonist RX811059. In contrast, UK-14,304 was inhibited only by RX811059. Either prazosin or RX811059 reduced the effect of the mixed agonist adrenaline. In spinal dogs, the noradrenaline-evoked fall in nasal cavity pressure was reduced by either prazosin or RX811059. Prazosin attenuated markedly the nasal vasoconstrictor response to electrical stimulation of postganglionic fibres emerging from the superior cervical ganglion (SNS) whereas RX811059 was ineffective. Administration of the neuronal re-uptake inhibitor cocaine potentiated the effect of i.a. noradrenaline but reduced marginally the maximal response to SNS. After cocaine, RX811059 enhanced the effect of SNS and attenuated the response to noradrenaline. Prazosin reduced effectively the responses to both SNS and noradrenaline after cocaine. Pretreatment with the alpha 2-agonist UK-14,304 did not affect the response to noradrenaline in the nasal cavity but evoked a persistent (up to 2 h) reduction in the response to SNS. RX811059 antagonized the inhibitory effect of UK-14,304. These results demonstrate that both postjunctional alpha 1- and alpha 2-adrenoceptors mediating vasoconstriction are present in the canine nasal mucosa. In addition, sympathetic neurones innervating the nasal mucosa are characterized by a very efficient re-uptake process and contain prejunctional alpha 2-adrenoceptors.

Scanning electron microscopy of nasal arterioles effected by vasoactive agents

Morphological changes in nasal blood vessels induced by alpha- and beta-adrenergic and cholinergic agonists were studied under a scanning electron microscope after removal of extracellular connective tissue and the basal lamina. Arterioles were constricted and dilatated following topical application of alpha-adrenergic and cholinergic agonists. Distinctive morphological changes were observed on their smooth muscle cells. Smooth muscle cells of constricted arterioles had a rugged surface with numerous fine invaginations. However, in dilatated arterioles the cells had a smooth surface and intercellular spaces were clearly revealed. No remarkable changes were produced in smooth muscle cells by the beta-adrenergic agonist. It is concluded that nasal arterioles are sensitive to alpha-adrenergic and cholinergic stimulation but not to beta-adrenergic stimulation.

Control of mucoglycoprotein output from the rabbit nose

A method for the collection of rabbit nasal washings to analyse outputs of mucous glycoproteins is described. The radiolabels sodium [35S]sulphate and [3H]glucose are bound to the glycoproteins. The release of bound 35S and 3H was enhanced by cervical sympathetic nerve stimulation. Adrenoceptor agonists (phenylephrine, dobutamine and salbutamol) given I.V. increased the output of 35S, and the last two drugs increased the output of 3H. The blocking effects of thymoxamine and propranolol on these responses are described. Pilocarpine (given I.V. or intranasally) produced large increases in 35S release; histamine had little effect. Irritants (ammonia and cigarette smoke) and diluted serum or plasma, given intranasally, produced large increases in 3H output, and sometimes enhanced 35S release. Radiolabelled nasal washings fractionated on Sepharose CL-4B gel chromatography columns formed two peaks, with most of the radioactivity in the high molecular weight (mucous glycoprotein) peak.

Chronic paroxysmal hemicrania: salivation, tearing and nasal secretion

Autonomic functions have been studied in seven patients with chronic paroxysmal hemicrania (CPH). A test battery comprising tearing, salivation and nasal secretion was employed. Under basal conditions these parameters did not differ significantly from those in a control group. After stimulation with pilocarpine the patients responded rather inhomogeneously. This test battery may therefore help find and classify subgroups of these types of patients. During attacks, there is a clear discrepancy between minimal salivation on the one hand and the marked increase in tearing, nasal secretion and sweating on the other. CPH attacks may be associated with an increased firing of sympathetic impulses to the different organs. In the event of a uniform type of autonomic firing taking place during attack, these findings may suggest a different innervation pattern for the salivary glands compared to the other glands involved. The innervation pattern of these secretory organs may seem to be more intricate and sophisticated than hitherto assumed.

Adrenoceptors in the control of human nasal mucosal blood flow

The blood flow in the human nasal mucosa is controlled by the functional state of the resistance vessels. This blood flow was studied by means of the 133Xe washout method. Using topical application of drugs that stimulate or block adrenoceptors, including clinical doses of nasal decongestants, we classified the adrenoceptors of the resistance vessels in the mucosa. The results suggest that stimulation of alpha2-adrenoceptors causes a reduction of nasal mucosal blood flow; stimulation of alpha1- and beta2-adrenoceptors seems to have no significant effects. Drugs that selectively stimulate alpha2-adrenoceptors, as well as those with preference for alpha1-adrenoceptors, cause nasal decongestion. To avoid the negative effects of a nasal mucosal blood flow reduction, it is suggested that a nasal decongestant with an alpha1-adrenoceptor stimulating effect should be preferable to a drug acting mainly on alpha2-adrenoceptors, provided that the decongestive effects are equal.

Substance-P-containing nerve fibers in the nasal mucosa

Nerve fibers displaying SP immunoreactivity were detected in the nasal mucosa of several mammals. The fibers were seen around small blood vessels, seromucous glands, and beneath and sometimes within the surface epithelium. In the pterygopalatine ganglion and the trigeminal ganglion, known to innervate the nasal mucosa, SP-positive nerve cell bodies were seen. Sympathetic denervation with 6-hydroxydopamine (6-OHDA) or bilateral cervical sympathectomy did not visibly affect the distribution of SP fibers in the nasal mucosa in mice or rats. The findings are compatible with the view that the bulk of SP fibers to the nasal mucosa derive from the trigeminal ganglion with a possible contribution from the pterygopalatine ganglion.

Innervation of the mucosa of rabbit maxillary sinus. II. Demonstration of catecholamine fluorescence and acetylcholinesterase activity

The innervation of the rabbit maxillary sinus mucosa has been studied with histochemical techniques, using the glyoxylic acid-induced fluorescence for the demonstration of catecholamines and the acetylcholinesterase method. A dense acetylcholinesterase-positive nerve plexus can be demonstrated around the secretory end-pieces, the efferent ducts, the blood vessels in the lamina propria, and rarely but regularly in the ciliated epithelium. A doubtless identification of these nerve fibres to be cholinergic does not seem possible. The adrenergic innervation is lacking within the epithelium, but can be seen near the muscle layers around blood vessels and in the lamina propria. An additional sympathetic control of the glandular activity is not excluded.

A method for evaluating the effect of pharmacological substances on mucociliary activity in vivo

A test model for in vivo studies of the effect of pharmacological substances on mucociliary activity in the rabbit maxillary sinus is presented. The method permits administration of pharmacological substances and recording of the mucociliary activity under conditions that mimic the physiological situation very closely. The test substances are given intra-arterially. Using a photoelectric technique the mucociliary activity is recorded from a small and limited area of the mucous membrane. There is minimal exposure to external stimuli since normal sinus ventilation is retained. Various factors which may influence the results, e.g. the anesthesia, movements from cardiac and respiratory activity, and the volumes and injection velocities of test doses, are analysed and discussed. When the animal model was tested with serotonin, ATP, and certain cholinergic and adrenergic agents, it was found to be reliable. It permitted easy detection of changes in the mucociliary activity and gave reproducible results.

Neurophysiological mechanism of shrinkage of nasal mucosa induced by exercise

Change of serum norepinephrine level and nasal patency were measured in 10 normal volunteers during exercise and effect of unilateral cervical sympathetic ganglion block on exercise-induced shrinkage of nasal mucosa was evaluated. Serum norepinephrine elevated markedly after 10-min exercise. Unilateral blocking of cervical ganglion completely inhibited mucosal shrinkage induced by exercise in 8 of 10 subjects. Mucosal shrinkage during exercise in these subjects was assumed to be mediated through cervical sympathetic ganglion, and not by increase in circulating cathecolamine. However, in 2 subjects, moderate shrinkage of the nasal mucosa was observed in 10-min after initiation of exercise. It was impossible to rule out some effect of circulating cathecolamine on the capacitance vessels of the nasal mucosa completely.

The origin of vasoactive intestinal polypeptide (VIP) nerves in the feline nasal mucosa

The feline nasal mucosa is richly supplied with vasoactive intestinal polypeptide (VIP) immunoreactive nerve fibres. The nerves occur in the subepithelial connective tissue, around small blood vessels and around the acini of seromucous glands. The ptergopalatine ganglion contains numerous VIP immunoreactive nerve cell bodies among non-reactive ones. Extirpation of the ganglion results in an almost complete disappearance of VIP-containing nerves in the nasal mucosa, while sectioning of the preganglionic nerve (Vidian nerve) does not affect the number of nasal VIP nerves. Hence the bulk of VIP nerve fibers in the nasal mucosa derive from cell bodies located in the pterygopalatine ganglion.

Innervation of the feline eustachian tube

The distribution of adrenergic, cholinergic and peptidergic nerves in the feline eustachian tube was studied using histochemical techniques. Adrenergic, acetylcholinesterase-positive and vasoactive intestinal polypeptide immunoreactive nerves were numerous in the tubal wall. All three types of nerve fibers occurred in the subepithelial layer, around small blood vessels and around the acini of seromucous glands. No nerves displaying substance P or enkephalin immunoreactivity were observed.