Effects of neurokinin A and calcitonin gene-related peptide on mucociliary activity in rabbit maxillary sinus.

Substance P (SP) released from sensory C-fibers in the airways increases the mucociliary (m.c.) activity in the rabbit maxillary sinus. The purpose of the present study was to investigate the m.c. effects of two other neuropeptides, coexisting with SP in sensory neurones, neurokinin A (NKA) and calcitonin gene-related peptide (CGRP). NKA increased the m.c. activity dose-dependently (dose range 0.1-10.0 micrograms/kg, 88 pmol to 8.8 nmol/kg), the maximum increase being 41.9 +/- 2.6%. The effect was inhibited by pretreatment with the tachykinin antagonist (D-Pro2,D-Trp7,9)SP, but not with atropine or hexamethonium. Thus NKA released from sensory C-fibers may contribute to the non-cholinergic increase of m.c. activity observed after C-fiber stimulation. In contrast CGRP did not influence the m.c. activity. Neither did it influence the responses to NKA or SP. It is concluded that CGRP is unlikely to be involved in the control of m.c. function.

Substance P antagonists and mucociliary activity in rabbit.

Substance P (SP) is known to accelerate mucociliary (m.c.) activity in the rabbit maxillary sinus in vivo. The physiological significance of this finding was investigated by testing three putative SP antagonists. [Arg5, D-Trp7,9, Nle11]SP5-11 could not be used as an antagonist because it stimulated m.c. activity. [D-Arg1, D-Trp7,9, Leu11]SP had no effect on the m.c. activity changes induced by SP. [D-Pro2, D-Trp7,9]SP was found to be an effective antagonist, 1 mg/kg of this drug reversibly inhibiting both the effects of 0.1 micrograms/kg SP and the stimulating effect of 1.0 micrograms/kg bradykinin and 30.0 micrograms/kg capsaicin; the stimulating effect of 0.5 micrograms/kg methacholine was not inhibited. It is suggested that bradykinin and capsaicin stimulate m.c. activity at least partly by releasing SP. The results of this investigation also support the view that the accelerating effect of SP on m.c. activity reflects physiological SP-mediated protective mechanisms in the airways. It is concluded that [D-Pro2,D-Trp7,9]SP is a useful pharmacological tool for studying the role of SP in the control of m.c. activity in rabbits.

Effects of halothane on mucociliary activity in vivo.

The effect of halothane on mucociliary activity in the rabbit maxillary sinus in vivo was recorded photoelectrically. Administration of halothane (1%, 2% or 4%) into the maxillary sinus induced a temporary acceleration of mucociliary activity. The peak increase (39.1% +/- 9.1%, p < 0.05, n = 5) was seen after the 4% concentration. Long-term exposure (60 minutes) of the maxillary sinus to halothane (2%) first induced an increase of 28.4% +/- 4.6% (p < 0.05, n = 6), lasting approximately four minutes, and followed after about 15 minutes by a decrease of mucociliary activity. The maximum decrease during the 60-minute period was 19.6% +/- 2.8% (p < 0.05, n = 6). Mucociliary activity returned to its baseline level approximately 25 minutes after withdrawal of halothane. Halothane delivered to the rabbit through a tracheal cannula at 1.1% for 60 minutes did not impair mucociliary activity in the maxillary sinus. On the contrary, it initially stimulated mucociliary activity, 19.9% +/- 2.7% (p < 0.05, n = 5). There was also an initial increase in respiratory rate from 62 +/- 7.3 to 89 +/- 12.9 breaths per minute (p < 0.05), which was noticeable after approximately 10 seconds and lasted 4 to 5 minutes. The dose-dependent increase in mucociliary activity seen after short-term exposure to halothane is probably due to stimulation of afferent C fibers, because halothane may be considered an airway irritant. The reversible depressant effect seen after 15 minutes of exposure is in accordance with findings in previous studies in vitro. The mechanism by which halothane impairs mucociliary activity is at present not known. However, halothane administered to the lower airways does not impair mucociliary activity in the maxillary sinus, indicating that halothane affects the ciliated epithelium directly and that the state of anesthesia itself has no effect on mucociliary activity.

VIP potentiates cholinergic effects on the mucociliary system in the maxillary sinus.

The neuropeptide vasoactive intestinal polypeptide (VIP), which is found in a population of cholinergic parasympathetic neurons in the airways, has no effects per se on mucociliary activity. In order to test the hypothesis that VIP may modulate cholinergic regulation of the mucociliary system, VIP was infused intraarterially (8.4 pmol/kg/min), and the response to challenges with methacholine in the maxillary sinus of rabbits were recorded with a photoelectric technique. Occurrence of VIP-like immunoreactivity in the rabbit maxillary sinus, maxillary nerve, and sphenopalatine ganglion was investigated. Immunoreactivity against VIP was found in nerve fibers in the subepithelial layer of the maxillary sinus and in numerous nerve cell bodies in the sphenopalatine ganglion. Infusion of VIP potentiated the mucociliary increase induced by methacholine. The mucociliary wave frequency change increased from 6.1% +/- 1.7% to 13.3% +/- 3.9% (0.01 micrograms/kg methacholine), from 11.6% +/- 3.6% to 18.8% +/- 2.2% (0.05 micrograms/kg) and from 17.0% +/- 3.0% to 27.4% +/- 3.6% (0.1 micrograms/kg). Both peak responses and response durations increased during infusions. In contrast, the vasodilating agent papaverine sulphate did not influence the mucociliary response to methacholine. The modulating effect of VIP on the mucociliary system, taken together with the morphologic observations, suggest that VIP may have a physiologic role in the regulation of the mucociliary system in the maxillary sinus.

Air humidity and mucociliary activity.

The relationship between varying humidity levels in the surrounding air and the mucociliary activity in rabbit trachea has been investigated. At a relative humidity (R.H.) above 70% the risk for ciliestasis is very small in the temperature range between 34 C and 40 C. At 37 C ciliestasis is not obtained until a relative humidity (R.H.) of 50% has been reached. The critical border is reached already at 60% R.H. if the temperature is 40 C. At 37 C and a decrement from 90% to 60% R.H. the mucociliary wave frequency was reduced by 30%, but at 40 C the corresponding reduction was 60%.

Histamine stimulation of mucociliary activity in the rabbit maxillary sinus.

The in vivo effect of histamine on mucociliary activity in the rabbit maxillary sinus was investigated by injecting histamine into the maxillary artery and recording the responses with a photoelectric technique. Histamine stimulated the mucociliary activity dose-dependently in the dose range 10 to 1,000 micrograms/kg. The maximum response was 31.6% +/- 3.7% at a dose of 50 micrograms/kg. The histamine-induced stimulation of the mucociliary activity was characterized by a short latency with a peak response within 1 to 2 minutes and a slow decline lasting about 5 minutes. The response displayed tachyphylaxis. Cholinergic blockade with atropine did not affect the response to histamine. Blockade of H1 receptors with pyrilamine abolished the response to histamine, whereas blockade of H2 receptors with cimetidine was without effect. The H2 agonist dimaprit failed to stimulate the mucociliary activity. It is concluded that histamine stimulates the mucociliary activity in the rabbit maxillary sinus via H1 receptors.

Cyclic adenosine monophosphate stimulation of mucociliary activity in the upper airways in vivo.

Xanthine derivatives are known to accelerate mucociliary transport in the lower airways, probably by preventing degradation of cyclic adenosine monophosphate (cAMP) and thereby increasing its intracellular concentration. The purpose of this study was to investigate the effects of cAMP on mucociliary activity in the upper airways. The effect on the mucociliary activity in the rabbit maxillary sinus of the xanthine derivatives theophylline and enprophylline was compared to that of the cAMP analog dibutyryl cAMP. The compounds were administered into the maxillary artery, and the response was recorded with a photoelectric technique. Infusions of theophylline (1.0 and 10 mg/kg) increased mucociliary activity (22.8% +/- 5.9%, n = 6, and 21.6% +/- 4.9%, n = 7, p < .05, respectively). Infusions of enprophylline (1.0 and 10.0 mg/kg) accelerated mucociliary activity (at the highest dosage tested, 24.3% +/- 4.1%). Infusions of dibutyryl cAMP (0.1 and 1.0 mg/kg) stimulated mucociliary activity, with the maximum increase (20.1% +/- 3.0%, n = 13, p < .05) being observed at a dosage of 0.1 mg/kg. The infused substances increased mucociliary activity within 1 minute after the start of the infusion, the duration of the response being approximately 20 minutes for theophylline, 22 minutes for enprophylline, and 12 minutes for dibutyryl cAMP. The present results support the view that cAMP is involved in regulating mucociliary activity in the upper airways. It remains to be elucidated whether xanthines such as theophylline and enprophylline are beneficial in upper airway disease in which mucociliary function is impaired (eg, chronic sinusitis).

Effects of neuropeptides on mucociliary activity.

The effects of four neuropeptides, vasoactive intestinal polypeptide, enkephalin, bombesin, and substance P, on mucociliary activity in the rabbit maxillary sinus were investigated in vivo. The peptides were administered via the feeding artery (arteria maxillaris), and the resulting effects were registered with a noninvasive photoelectric technique. The peptides were tested in the dose range 0.0001 to 10 micrograms/kg body weight. The following results were observed: 1) vasoactive intestinal polypeptide and enkephalin did not influence mucociliary activity; 2) bombesin had only a slight accelerating effect on the mucociliary activity at doses of 0.1 to 10 micrograms/kg; and 3) substance P markedly accelerated the mucociliary activity in a dose-dependent manner in the dose range 0.01 to 10 micrograms/kg, the maximal increase being about 50%. The effect of substance P was atropine-resistant, and probably acted directly on the mucosa.

The influence of varying air humidity on mucociliary activity.

The influence of varying humidity levels in the air surrounding the mucous membrane of rabbit tracheae has been investigated in vitro at 34 degrees C, 37 degrees C and 40 degrees C. The following results were obtained: (1) The average mucociliary wave frequency was linearly reduced following decreasing levels of relative humidity (r.h.) from 90% to 20%. (2) A temperature of 40 degrees C was more detrimental to the mucociliary function than that of 34 degrees C and 37 degrees C (body temperature) at decreasing levels of r.h. (3) At decreasing levels of r.h. the duration of experiments with preservation in recordable activity ("mucociliary survival time") was significantly shorter (p smaller than 0.05) between 50% and 40% r.h. than between 60% and 50% r.h.

Antidromic nerve stimulation accelerates mucociliary activity in rabbit maxillary sinus.

The neuropeptide substance P (SP) is released from unmyelinated C-fibres in sensory nerves by antidromic nerve stimulation. In order to study the effect on mucociliary (m.c.) activity, the isolated distal end of the maxillary nerve was stimulated electrically (8 V, pulse rate 10 Hz, 5 ms pulses) 2-4 min, while the m.c. wave frequency in the maxillary sinus was recorded by a photoelectric technique. The m.c. wave frequency increased during stimulation by 35.4 +/- 4.9% (range 22.0-62.2%). Following pretreatment with atropine the m.c. activity increased by only 20.0 +/- 1.3% (range 14.9-21.9%) indicating that part of the response was mediated via stimulation of muscarinic receptors. The cholinergic part of the response is presumably secondary to release of SP since the SP antagonist [D-Pro2, D-Trp7,9]SP abolished the effect of nerve stimulation. Sympathetic ganglionectomy did not influence the response to antidromic nerve stimulation. It is concluded that antidromic stimulation of the maxillary nerve accelerates m.c. activity through a dual mechanism, involving release of SP, or SP-like peptides, from sensory C-fibre nerve endings as well as release of acetylcholine.

Bradykinin accelerates mucociliary activity in rabbit maxillary sinus.

The in vivo effect of bradykinin on mucociliary (m.c.) activity in the rabbit maxillary sinus was investigated by administering the substance (0.01-10.0 micrograms/kg) via arteria maxillaris and recording the responses with a non-invasive photoelectric technique. Bradykinin accelerated the m.c. activity in a dose-dependent manner in the dose range 0.05-10.0 micrograms/kg. While the action of bradykinin was resistant to pretreatment with indomethacin 10.0 mg/kg, it was considerably weakened by the substance P antagonist [D-Pro2, D-Trp7,9]SP 1 mg/kg. The initial effect of bradykinin was also suppressed by atropine, suggesting that bradykinin accelerates m.c. activity by a dual mechanism comprising both SP and acetylcholine. Bradykinin probably stimulates a reflex arc in the airways involving afferent SP neurons and efferent post-ganglionic parasympathetic neurons.

Cholinergic and C-fibre mediated mechanisms in the stimulation of mucociliary activity induced by prostaglandins and histamine.

The involvement of cholinergic and C-fibre mediated mechanisms in the stimulation of mucociliary activity induced by prostaglandins and histamine was investigated in vivo in the rabbit maxillary sinus with a photoelectric technique. The prostaglandins E, (PGE,) and F2(2) alpha (PGF2 alpha) in dose of 0.1 microgram/kg and 10 micrograms/kg respectively stimulated the mucociliary activity in a biphasic fashion, with a small initial response during the first 1-2 min and a later maximum response after 3-4 min. These effects were resistant to atropine and to the SP antagonist (D-Pro2, D-Trp7,9)SP. The small initial response was blocked by pretreatment with high doses of capsaicin (13 mg i.a.), while the maximum response was unaffected. This indicates that the mucociliary responses induced by PGE, and PGF2 alpha involve capsaicin-sensitive C-fibres but that neither acetylcholine nor substance P were responsible. Histamine (50 micrograms/kg) stimulated mucociliary activity in the rabbit maxillary sinus and the effect was abolished by pretreatment with high doses of capsaicin and reduced by the SP antagonist (D-Pro2, D-Trp7,9)SP. This indicates that the histamine-induced stimulation of mucociliary activity involves capsaicin-sensitive C-fibres and that the effect might be mediated by substance P.

Nasal exposure to airway irritants triggers a mucociliary defence reflex in the rabbit maxillary sinus.

The effect on mucociliary (m.c.) activity in the rabbit maxillary sinus of cigarette smoke and ammonia (NH3) vapour delivered through a tracheal cannula or as nasal challenges was investigated by a photo-electric technique, and compared with simultaneously induced changes in the respiratory rate. Neither irritant had any effect on m.c. activity in the sinus after tracheo-bronchial exposure. However, the respiration rate was increased by NH3 vapour (2.5 ml, diluted 1:1 with room air) and neat cigarette smoke (10 ml) by 76.9% and 24.3% respectively (median values). In contrast, nasal challenges with both irritants increased m.c. activity by 24.1% (NH3) and 19.1% (cigarette smoke), and reduced the respiration rate by 31.0% (NH3) and 28.4% (cigarette smoke) (median values). NH3 vapour sometimes produced an apnea proper. Identical results were obtained in laryngectomized rabbits, indicating that laryngeal afferents were not involved in the responses. Moreover, topical application of the C-fibre stimulant capsaicin mimicked the effects produced by the airway irritants. It is concluded that nasal exposure to irritants triggers at least two different protective reflexes. One is the increase of m.c. activity in the upper airways involving sensory C-fibres and the other the apneic reflex of Kratschmer.

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.

Effects of the parasympathomimetic drug methacholine and its antagonist atropine on mucociliary activity.

The effect on the mucociliary (m.c.) activity of the parasympathomimetic drug methacholine and its antagonist atropine was studied with the aid of a newly developed animal test model, designed for evaluating the effect of pharmacological substances on the m.c. wave frequency. Methacholine i.a. (0.01-2 micrograms/kg) was found to give a dose-dependent acceleration of the m.c. wave frequency, and the threshold dose 0.03 +/- 0.02 (+/- S.D.) micrograms/kg is suggested to be within physiological limits. The anticholinergic drug atropine i.a. (0.05-0.5 mg/kg) did not influence the basal m.c. wave frequency, but a dose of 0.2 mg/kg reduced or abolished the responses to methacholine (0.05-2 micrograms/kg). These results indicate that the basal m.c. activity functions independently of parasympathetic activity in anesthetized animals, that parasympathomimetic drugs influence the m.c. activity and that the effects of these drugs can be reduced or blocked by atropine.

Effects of sympathomimetic agonists and antagonists on mucociliary activity.

The effect on the mucociliary (m.c.) wave frequency of sympathomimetic agonists and antagonists was studied in the maxillary sinus in anesthetized rabbits. The non-selective beta-adrenoceptor agonist isoprenaline (0.005-10 micrograms/kg i.a.) and the selective beta2-adrenoceptor agonist salbutamol (0.01-10 micrograms/kg, i.a.) induced a dose-dependent acceleration of the m.c. wave frequency, whereas the beta1-adrenoceptor agonist prenalterol (1-200 micrograms/kg, i.a.) did not influence the basal m.c. activity. The selective alpha1-adrenoceptor agonist phenylephrine (0.01-20 micrograms/kg, i.a.) and the selective alpha2-adrenoceptor agonist oxymetazoline (0.001-1 microgram/kg, i.a.) both induced a dose-dependent retardation of the m.c. wave frequency. The non-selective beta-adrenoceptor antagonist propranolol (2-200 micrograms/kg, i.a., and 1 mg/kg, i.v.) and the non-selective alpha-adrenoceptor antagonist phentolamine (0.1-1 000 micrograms/kg, i.a.) had no influence on the basal m.c. wave frequency. Propranolol (1-2 mg/kg, i.v.) reduced the effect of isoprenaline and salbutamol (both in the dose range of 0.01-10 micrograms/kg, i.a.) and similarly phentolamine (0.2 and 1 mg/kg, i.a.) reduced the effect of oxymetazoline (0.01-10 microgram/kg, i.a.). It was concluded that during basal conditions in the anesthetized rabbit the m.c. activity functions independently of sympathetic activity and that sympathomimetic agonists acting on beta2-adrenoceptors accelerate the wave frequency, whereas sympathomimetic agonists acting on alpha1 and alpha2-adrenoceptors have a retarding effect, all in a dose-dependent manner.

The effect of neuropeptide Y on mucociliary activity in the rabbit maxillary sinus.

The effect of neuropeptide Y (NPY) on mucociliary activity in the rabbit maxillary sinus was investigated in vivo by injecting NPY at increasing dosages into the maxillary artery, response being recorded photoelectrically. At dosages of 0.1-5.0 micrograms/kg, NPY reduced mucociliary activity dose-dependently, the maximum decrease being 14.6 +/- 1.8%, at a dosage of 5.0 micrograms/kg. The NPY-induced reduction of the mucociliary activity manifested brief latency, the peak effect occurring within 3 min followed by a slow return to the baseline value 4-9 min after injection. The response of mucociliary activity to NPY remained unaffected by pretreatment with the alpha-adrenergic antagonists yohimbine (alpha 2) at 100.0 micrograms/kg and phentolamine (alpha 1 + alpha 2) at 0.2-1.0 mg/kg, indicating that the effect of NPY is not mediated via alpha-receptors. Pretreatment with the calcium antagonist nifedipine at 100.0 micrograms/kg inhibited the effect of NPY, suggesting that the NPY-induced decrease may be calcium dependent.

The influence of leukotrienes and platelet activating factor on mucociliary activity in the rabbit maxillary sinus.

Inflammatory mediators released in the airways during allergic reactions can affect the mucociliary system. Leukotrienes and platelet activating factor have been shown to affect the mucociliary activity in various cell preparations. The in vivo effects of these inflammatory mediators on mucociliary activity in rabbit maxillary sinus were investigated using a photoelectric technique. Leukotrienes C4 and D4 in the dose range 0.01-10.0 nmol/kg did not alter mucociliary activity significantly, either when given as bolus injections or as intraarterial infusions. Platelet activating factor had no effect in the dose range 0.001-0.1 nmol/kg. A dose of 1.0 nmol/kg increased mucociliary activity by 20.2 +/- 5.5% but produced adverse respiratory and circulatory effects at the same time. It is concluded that the inflammatory mediators leukotrienes C4, D4 and platelet activating factor have no essential regulatory influence on mucociliary activity in the upper airways of the rabbit.

The effects of prostaglandins E1, E2 and F2 alpha on mucociliary activity in the rabbit maxillary sinus.

The in vivo effects of prostaglandins E1, E2 and F2 alpha on mucociliary activity in the rabbit maxillary sinus were investigated using a photoelectric technique. Prostaglandins E1 and F2 alpha both accelerated the mucociliary wave frequency in a dose-dependent fashion. For prostaglandin E1 the maximum increase was 17.4 +/- 2.6% (0.1 micrograms/kg), for prostaglandin F2 alpha it was 24.1 +/- 3.0% (10 micrograms/kg). The effects of prostaglandin E2 was inconsistent. Although some doses stimulated mucociliary activity, the effects were not reproducible. Inhibition of phosphodiesterase with theophylline did not alter the response to exogenous prostaglandin E1, nor did inhibition of endogenous prostaglandin synthesis with indomethacin affect the basal mucociliary activity or the response to exogenous prostaglandin E1. The present findings suggest that the tested prostaglandins are of minor importance for regulating mucociliary function in the rabbit maxillary sinus.

The morphological basis for the effect of substance P on mucociliary activity in rabbit maxillary sinus.

The mucociliary (m.c.) activity in rabbit maxillary sinus is accelerated by the neuropeptide substance P (SP). The morphological basis for this mechanism was investigated by immunocytochemistry using monoclonal antibodies directed against SP. SP-like immunoreactivity was found in nerve fibres in the subepithelial layer of the sinus mucosa, in the maxillary nerve, and in nerve endings close to nerve cell bodies in the sphenopalatine ganglion. Thus, there is morphological evidence in the rabbit that SP plays a role in the regulation of m.c. activity. The results also support the view that the rabbit maxillary sinus is a suitable experimental model for studying SP effects in the airway mucosa.