The innervation of mammalian bronchial smooth muscle: the localization of catecholamines and cholinesterases

Electroacupuncture reduced airway inflammation by activating somatosensory-sympathetic pathways in allergic asthmatic rats

BACKGROUND

Electroacupuncture (EA) treatment is efficacious in patients with respiratory disorders, although the mechanisms of its action in lung-function protection are poorly understood. This study aimed to explore the neuroanatomical mechanisms of EA stimulation at the BL13 acupoint (Feishu, EA-BL13) improvement in asthma.

METHODS

Allergic asthma was induced by intranasal 2.0% ovalbumin (OVA) instillation combined with intraperitoneal injection of the 10.0% OVA. The levels of interleukin (IL)-4 and IL-5 were detected by enzyme-linked immunosorbent assay. Hematoxylin and eosin and periodic acid-schiff stain were used to evaluate inflammatory cell infiltration and mucus secretion. Cellular oncogene fos induction in neurons after EA stimulation was detected by immunofluorescent staining. The mRNA expression levels of adrenergic receptors were quantified with real-time polymerase chain reaction.

RESULTS

EA improved airway inflammation and mucus secretion mainly by activating somatosensory-sympathetic pathways (P <0.001). Briefly, the intermediolateral (IML) nuclei of the spinal cord received signals from somatic EA stimulation and then delivered the information via the sympathetic trunk to the lung. Excited sympathetic nerve endings in lung tissue released large amounts of catecholamines that specifically activated the β2 adrenergic receptor (β2AR) on T cells (P <0.01) and further decreased the levels of IL-4 and IL-5 (P <0.001) through the cyclic adenosine monophosphate/protein kinase A signaling pathway.

CONCLUSION

This study provided a new explanation and clinical basis for the use of EA-BL13 as a treatment for allergic asthma in both the attack and remission stages and other respiratory disorders related to airway inflammation.

Autonomic neural control of intrathoracic airways

Autonomic neural control of the intrathoracic airways aids in optimizing air flow and gas exchange. In addition, and perhaps more importantly, the autonomic nervous system contributes to host defense of the respiratory tract. These functions are accomplished by tightly regulating airway caliber, blood flow, and secretions. Although both the sympathetic and parasympathetic branches of the autonomic nervous system innervate the airways, it is the later that dominates, especially with respect to control of airway smooth muscle and secretions. Parasympathetic tone in the airways is regulated by reflex activity often initiated by activation of airway stretch receptors and polymodal nociceptors. This review discusses the preganglionic, ganglionic, and postganglionic mechanisms of airway autonomic innervation. Additionally, it provides a brief overview of how dysregulation of the airway autonomic nervous system may contribute to respiratory diseases.

Effects of cyclohexenonic long-chain fatty alcohol on diabetic rat trachea

In order to investigate the diabetes-associated neuropathy and prevent effects of cyclohexenonic long-chain fatty alcohol, a neurotrophic substance, in trachea, we studied its effect on streptozotocin-diabetic hyper-reactivity in the rat trachea. Diabetes was induced in 8-week-old male Sprague-Dawley rats by administering an intraperitoneal injection of streptozotocin (50 mg/kg). The rats were divided randomly into four groups and were maintained for four weeks: age-matched control rats, diabetic rats without treatment with cyclohexenonic long-chain fatty alcohol, and diabetic rats treated with cyclohexenonic long-chain fatty alcohol (2 and 8 mg/kg, i.p. every day). The serum glucose and insulin levels were determined, and the contractile responses of the trachea induced by carbachol and KCl were investigated. Treatment with cyclohexenonic long-chain fatty alcohol did not alter the rats' diabetic status, i.e., body weight, thickness of the trachea, serum glucose levels, and serum insulin levels, but significantly improved the diabetic-induced hyper-reactivity of the rat trachea in a dose-dependent manner. There was no significant difference in either the carbachol- or KCl-induced contractile forces between groups with or without mucosa in the functional studies. In histological examinations, thinning of cricoid cartilage, thickness of basal membrane, and degeneration, fragmentation of elastic fibers in the submucosal layer, and hypertrophy of smooth muscle bundle in the membranous wall of trachea were observed in the diabetic rat trachea, which were improved by treatment with cyclohexenonic long-chain fatty alcohol. Our data indicate that this drug can prevent hyper-reactivity in the diabetic trachea.

Effect of experimental diabetes on GABA-mediated inhibition of neurally induced contractions in rat isolated trachea

1. In the present study, we investigated the effect of GABA and selective GABA agonists and antagonists on neurally induced tracheal contractions in streptozotocin (STZ) diabetic rats. 2. Contractile responses to electrical field stimulation (EFS) in rat tracheal rings were completely abolished by atropine and tetrodotoxin, but were unaffected by the ganglion blocker hexamethonium, indicating that they were mediated via neuronal release of acetylcholine (ACh). 3. Contractions induced by EFS, but not by exogenous ACh, were inhibited by GABA and the selective GABA(B) receptor agonist baclofen, but not by the selective GABA(A) receptor agonist 3-aminopropane sulphonic acid. The inhibitory effects of GABA or baclofen were not affected by the GABA(A) antagonist bicuculline, but were significantly reversed by the GABA(B) antagonist phaclofen. 4. The inhibitory effects of both GABA and baclofen were found to be significantly greater in trachea from control rats compared with tissues from diabetic rats. 5. Non-adrenergic, non-cholinergic relaxation responses elicited by EFS in precontracted tracheal rings from diabetic and control rats were similar in magnitude and were unaffected by GABA or GABA analogues. 6. These results suggest that GABA decreases the response to EFS by directly inhibiting the evoked release of ACh through GABA(B) receptors in rat trachea and that STZ-induced diabetes causes an impairment in the inhibitory effect of GABA on neurally induced contractions in this tissue.

The effect of experimental diabetes on cholinergic neurotransmission in rat trachea: role of nitric oxide

We investigated the effect of nitric oxide (NO) on the responses of isolated tracheas to acetylcholine and to electrical field stimulation in streptozotocin-diabetic and controls rats. The contractile responses to acetylcholine were neither different nor affected by the NO synthase blocker, N(omega)-nitro-L-arginine methyl ester (L-NAME), in the two groups. Diabetic rat tracheas were supersensitive to field stimulation. L-NAME enhanced field stimulation-induced contractions at low frequencies in control rat tracheas, but had no effect in diabetic rat tracheas. After L-NAME treatment, there was no difference in sensitivity to field stimulation between the groups. The relaxation responses to sodium nitroprusside in acetylcholine-precontracted tracheas were not different between the groups. However, diabetic rat trachea was supersensitive to the relaxant effect of sodium nitroprusside on contractile responses to field stimulation. These results suggested that the increase in sensitivity to field stimulation in tracheas from diabetic rats might be due to impairment in the production and/or release of an endogenous NO-like factor.

Central control of the cardiovascular and respiratory systems and their interactions in vertebrates

This review explores the fundamental neuranatomical and functional bases for integration of the respiratory and cardiovascular systems in vertebrates and traces their evolution through the vertebrate groups, from primarily water-breathing fish and larval amphibians to facultative air-breathers such as lungfish and some adult amphibians and finally obligate air-breathers among the reptiles, birds, and mammals. A comparative account of respiratory rhythm generation leads to consideration of the changing roles in cardiorespiratory integration for central and peripheral chemoreceptors and mechanoreceptors and their central projections. We review evidence of a developing role in the control of cardiorespiratory interactions for the partial relocation from the dorsal motor nucleus of the vagus into the nucleus ambiguus of vagal preganglionic neurons, and in particular those innervating the heart, and for the existence of a functional topography of specific groups of sympathetic preganglionic neurons in the spinal cord. Finally, we consider the mechanisms generating temporal modulation of heart rate, vasomotor tone, and control of the airways in mammals; cardiorespiratory synchrony in fish; and integration of the cardiorespiratory system during intermittent breathing in amphibians, reptiles, and diving birds. Concluding comments suggest areas for further productive research.

Influence of TASP-V, a novel neuropeptide Y (NPY) Y2 agonist, on nasal and bronchial responses evoked by histamine in anaesthetized pigs and in humans

1. In nine anaesthetized pigs we have studied the influence of intranasal or intrabronchial pretreatment with TASP-V, a neuropeptide Y (NPY) Y2 agonist formed by the attachment of NPY 21-36 to a template-assembled synthetic peptide (TASP), on the functional responses to subsequent intranasal or intrabronchial histamine challenge. 2. In a parallel study, subjective and objective nasal airway resistance (NAR) increase following intranasal histamine challenge was evaluated in 11 healthy volunteers after TASP-V or placebo pretreatment. 3. In pigs, increase in sphenopalatine blood flow induced by histamine dihydrochloride nasal spray (0.25 mg kg(-1) in 3 ml of saline) was significantly reduced by 65% (P<0.05) following intranasal pretreatment with 10 microg kg(-1) of TASP-V. Bronchoconstriction induced by histamine dihydrochloride nebulization (0.5 mg kg(-1) in 3 ml of saline) was significantly attenuated by 25 and 55% following aerosolized pretreatment with TASP-V analogue at 10 and 20 microg kg(-1), respectively. 4. In healthy volunteers, objective increase in NAR and reduction in nasal minimal cross section area (MCSA) induced by intranasal spray of histamine dihydrochloride (15 microg kg(-1) in 200 microl of saline) were significantly attenuated by 50% following local pretreatment with 1.275 microg kg(-1) of TASP-V when compared with saline. 5. It is concluded that intranasal or intrabronchial pretreatment with TASP-V reduced nasal obstruction and bronchoconstriction evoked by histamine challenge in the pig. In healthy human volunteers, this agent attenuated NAR increase and MCSA reduction induced by intranasal application of histamine.

Paradoxical facilitation of acetylcholine release from parasympathetic nerves innervating guinea-pig trachea by isoprenaline

1. Previous studies have provided evidence that activation of beta-adrenoceptors on cholinergic nerve terminals can inhibit neurotransmission in the airways. However, in most cases, this conclusion has been based on indirect evidence obtained from mechanical experiments where changes in airways smooth muscle tone were measured. 2. We have assessed whether modulation of cholinergic neurotransmission by beta-adrenoceptor agonists is due to a pre- or post-junctional action by investigating the effect of isoprenaline on contractile responses evoked by exogenous acetylcholine (ACh) and electrical field stimulation (EFS; 4 Hz, 40 V, 0.5 ms pulse width every 15 s), and on EFS-induced ACh release from cholinergic nerves innervating guinea-pig and human trachea. Furthermore, the subtype of beta-adrenoceptor which modulates neurotransmission and the potential role of cyclic AMP in this response were evaluated. 3. In guinea-pig trachea, isoprenaline (1 nM-1 microM) inhibited the contractile response evoked by exogenous ACh (1 microM) to a similar extent to that evoked by EFS (EC50 = 19.9 and 23 nM, respectively). 4. In epithelium-denuded guinea-pig strips treated with indomethacin (10 microM), isoprenaline significantly enhanced EFS-induced ACh release from cholinergic nerve terminals (by 36% at 0.3 microM). This effect was blocked by propranolol and ICI 118, 551 (each 0.1 microM). In contrast, isoprenaline failed to affect EFS-induced ACh release from parasympathetic nerves innervating human trachea. 5. To evaluate the role of cyclic AMP in the beta-adrenoceptor-induced facilitation of cholinergic neurotransmission, the effects of various cyclic AMP elevating drugs on ACh release were studied. Forskolin (10 microM) significantly augmented (by 17%) EFS-induced ACh release, an effect which was not reproduced by 1,9-dideoxyforskolin (10 microM) which does not activate adenylyl cyclase. Similarly, the cyclic AMP analogue, 8-bromo-cyclic AMP (1 mM) and cholera toxin (1 microgram ml-1) facilitated ACh output by 22 and 47% respectively, whereas prostaglandin E2 (PGE2, 0.1 nM-1 microM) inhibited this response (by 67% at 1 microM). 6. Zardaverine (10 microM), a dual inhibitor of the phosphodiesterase (PDE)3 and PDE4 isoenzyme families, did not affect EFS-induced ACh release and failed to facilitate the actions of either isoprenaline or PGE2. Similarly, neither SK&F 94120 (10 microM) nor rolipram (10 microM), selective inhibitors of PDE3 and PDE4 respectively, significantly affected the release of ACh in response to EFS. 7. The result of this study suggests that isoprenaline facilitates cholinergic neurotransmission in guinea-pig, but not human, trachea by activation of pre-junctional beta 2-adrenoceptors, an effect that may be mediated via activation of the cyclic AMP/cyclic AMP-dependent protein kinase cascade. Furthermore, the data presented herein illustrate the need to undertake direct measurements of neurotransmitter release when examining the effect of agents purported to act pre-junctionally.

The effect of xylazine on the isolated sheep trachea

The effect of xylazine on the isolated sheep trachea and its possible interactions with the alpha 2-adrenergic antagonist, atipamezole, and the anticholinergic agent, atropine, was studied. The mechanical responses of the tracheal preparations were recorded after exposing each one to cumulatively increasing concentrations of xylazine alone or in the presence of atipamezole or atropine. Xylazine exerted a concentration-dependent contractile effect, with a threshold concentration of 10(-7) M while the maximum activity was produced at a concentration of 10(-5) M (EC50 = 2.3 x 10(-7). This xylazine-induced contractile effect was inhibited by atipamezole, but not significantly modified by atropine. Thus, it is concluded that alpha 2-adrenoceptors exist in the sheep trachea and it is suggested that alpha 2-adrenoceptor agonists may act on airways in sheep directly through stimulation of peripheral alpha 2-adrenergic receptors and indirectly via central alpha 2-adrenergic receptor activation of parasympathetic tone.

Effect of atrial natriuretic peptide on bronchial tone in anesthetized rabbits

The effect of atrial natriuretic peptide (ANP) on histamine-induced bronchoconstriction was studied in vivo (in normoxic and in hypoxic rabbits) and in vitro. Thirty-two anesthetized rabbits, spontaneously breathing room air or 10% O2, received infusions of ANP (20, 40, or 80 ng/min/kg normoxia; 20 ng/min/kg hypoxia) or the vehicle for 100 min. After 75 min of ANP infusion, bronchoconstriction was induced inhaling histamine; respiratory resistance (Rrs) was measured prior to and until 20 min posthistamine. The results show that the histamine-induced increase in Rrs was significantly reduced by ANP 80 ng/kg/min in normoxia, and by ANP 20 ng/kg/min in hypoxia. In vitro, ANP had no effect on tracheal and bronchial smooth muscle precontracted with histamine or acetylcholine. These results show that ANP can decrease a histamine-induced bronchoconstriction in vivo but not in vitro, suggesting an indirect mechanism of action.

Muscarinic effect of atrial natriuretic peptide on rabbit airways

1. The aim of the present work was to investigate under which circumstances atrial natriuretic peptide (ANP) modulates airway resistance. 2. Of the six groups of rabbits (n = 5) studied, three received an infusion of ANP (80 ng min-1 kg-1 i.v.) for a period of 100 min, while the other three were infused with the vehicle. Before receiving the infusion of ANP or the vehicle, the animals were pretreated with atropine (0.5 mg kg-1 i.v.), propranolol (2 mg kg-1 i.v.) or not pretreated. After 75 min of infusion of ANP, bronchoconstriction was induced by inhalation of histamine. Respiratory resistance (Rrs) was measured before and 3, 5, 10, 15 and 20 min post-histamine challenge. 3. Following 75 min of ANP infusion, plasma ANP concentration increased from 153 +/- 52 (mean +/- s.e.mean) to 1441 +/- 203 pg ml-1 (P < 0.05) without affecting baseline Rrs. Control Rrs values (12.5-20.4 cmH2O l-1 s) were significantly increased following the inhalation of histamine (P < 0.001). By themselves, atropine, propranolol or ANP did not modify the histamine-induced increase in Rrs. However, when the animals were pretreated with atropine, ANP infusion significantly reduced the increase in Rrs induced by histamine (30 +/- 2 vs 51 +/- 6 cmH2O l-1 s; P < 0.05). 4. These data suggest that ANP has an indirect modulating effect on the airway smooth muscle and will decrease Rrs when muscarinic receptors are blocked.

Degradation of acetylcholine in human airways: role of butyrylcholinesterase

1. Neostigmine and BW284C51 induced concentration-dependent contractions in human isolated bronchial preparations whereas tetraisopropylpyrophosphoramide (iso-OMPA) was inactive on airway resting tone. 2. Neostigmine (0.1 microM) or iso-OMPA (100 microM) increased acetylcholine sensitivity in human isolated bronchial preparations but did not alter methacholine or carbachol concentration-effect curves. 3. In the presence of iso-OMPA (10 microM) the bronchial rings were more sensitive to neostigmine. The pD2 values were, control: 6.05 +/- 0.15 and treated: 6.91 +/- 0.14. 4. Neostigmine or iso-OMPA retarded the degradation of acetylcholine when this substrate was exogenously added to human isolated airways. A marked reduction of acetylcholine degradation was observed in the presence of both inhibitors. Exogenous butyrylcholine degradation was prevented by iso-OMPA (10 microM) but not by neostigmine (0.1 microM). 5. These results suggest the presence of butyrylcholinesterase activity in human bronchial muscle and this enzyme may co-regulate the degradation of acetylcholine in this tissue.

Neuronal control of airways smooth muscle

Sensory afferent nerves relay impulses from the airways to the central nervous system so that appropriate changes in bronchomotor tone and breathing patterns may occur. The dominant efferent control of airways smooth muscle is exerted via bronchoconstrictor parasympathetic cholinergic nerves. In some species this is opposed by bronchodilator sympathetic noradrenergic nerves. In addition, there exist both excitatory bronchoconstrictor and inhibitory bronchodilator non-adrenergic, non-cholinergic pathways. This review examines the role of the different branches of the autonomic nervous system in the control of airways smooth muscle tone with particular reference to modulation of these branches and the interactions which may exist between them.

Distribution of catecholamine-containing nerves on blood vessels of the rat trachea

This study was performed to determine the distribution of catecholamine-containing sympathetic nerves on blood vessels of the rat trachea. The glyoxylic acid method was used to visualize catecholamine-containing axons in tracheal whole mounts, and silicone vascular casts were used to elucidate the architecture of the vasculature. We also examined the relationship of these axons to the trachea's plexus of cholinergic nerves and ganglia, using tracheal whole mounts stained for acetylcholinesterase activity. We found that most catecholamine-containing axons were associated with arterioles located between cartilaginous rings or in the posterior membrane. In both regions, catecholamine-containing nerves were most abundant at the origin of terminal arterioles, which supplied the airway mucosa and smooth muscle. At the origin of these vessels, the fluorescent axons changed their orientation from longitudinal to circumferential. Few fluorescent axons were present beyond this region of the terminal arterioles, and none was found on capillaries or venules or on smooth muscle cells of the posterior membrane. Fluorescent axons were present in some tracheal ganglia but non enveloped neuronal cell bodies or had varicosities, and no ganglion cells had glyoxylic acid-induced fluorescence. Catecholamine-fluorescence was also present in clusters of small intensely fluorescent (SIF) cells, which were located in the adventitia of the posterior membrane and in the longitudinal nerve trunks which ran the length of the trachea. Pargyline pretreatment increased the fluorescence of axons and SIF cells but did not reveal a different distribution of these structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Serotonin immunoreactivity in the autonomic intrapulmonary ganglia of the fetal sheep

Using light microscopic immunohistochemistry, serotonin immunoreactivity was found in paraganglionic cells within pulmonary autonomic ganglia of fetal sheep at pseudoglandular and canalicular stages of lung development. Serotonin immunoreactive cells appeared individually or in clusters, and were occasionally seen around or in close contact with blood vessels.

Evidence for inhibition of sympathetic neurotransmission by endogenously released acetylcholine in the guinea-pig trachea

1. Interactions between pulmonary cholinergic and noradrenergic nerves were studied in the innervated tracheal tube preparation isolated from guinea-pigs anaesthetized with urethane. Relaxations of the trachealis smooth muscle in response to postganglionic stimulation of the sympathetic nerve were recorded as decreases in the intraluminal pressure of the tracheal tube after the pressure had been raised with the stable thromboxane-mimetic, U46619. In contrast, contractions following preganglionic stimulation of the vagal nerve trunk were recorded as increases in intraluminal pressure. 2. In approximately half of the preparations studied, concurrent stimulation of of the vagal nerve trunk the vagal nerve trunk inhibited relaxation responses elicited by stimulation of the sympathetic nerves. The vagi were stimulated at parameters which caused no change in intraluminal pressure, excluding the involvement of postjunctional mechanisms. 3. The effect of simultaneous stimulation of the sympathetic nerve trunk was studied on contractile responses evoked by preganglionic stimulation of the vagus nerve. In 80% of the preparations tested the vagal responses were inhibited. This inhibitory effect of sympathetic nerve stimulation was antagonized by propranolol. 4. The potassium channel agonist, cromakalim, endothelins 1 and 3 and the neuropeptides, vasoactive intestinal peptide, neurokinin A and substance P, did not significantly modulate sympathetic nerve-induced relaxations. 5. The anticholinesterase drug, physostigmine, induced a concentration-dependent increase in the intraluminal pressure of the tracheal tube and potentiated the postjunctional action of exogenously applied acetylcholine to contract the guinea-pig trachealis muscle. In the presence of higher concentrations of physostigmine both vagally-induced contractions and sympathetic nerve-induced relaxations were reduced. Atropine blocked both the inhibitory effect of physostigmine on sympathetic relaxations and its postjunctional contractile action on the trachealis smooth muscle.6. It is concluded that, in the guinea-pig trachea, acetylcholine released endogenously from pulmonary parasympathetic nerves, either by anticholinesterase drugs or in response to nerve stimulation, can inhibit transmission in the adjacent sympathetic nerves via activation of prejunctional muscarinic heteroreceptors, probably of the M3 subtype.

Evidence for prejunctional inhibitory muscarinic receptors on sympathetic nerves innervating guinea-pig trachealis muscle

1 Relaxation responses induced by stimulation of the postganglionic sympathetic nerve trunk were studied in the isolated, fluid-filled, innervated tracheal tube preparation of the guinea-pig. 2 The thromboxane-mimetic U46619, prostaglandin F2 alpha and histamine each caused concentration-dependent increases in the intraluminal pressure (ILP) of the fluid-filled tracheal tube, reflecting contraction of the trachealis muscle. Sympathetic nerve stimulation in the presence of the spasmogens caused relaxations which increased with increasing ILP. Relaxant responses evoked in the presence of these three spasmogens were comparable at any given ILP. 3 Muscarinic agonists caused concentration-dependent increases in ILP, pilocarpine being more potent than acetylcholine. Sympathetic nerve-induced relaxations were reduced in the presence of pilocarpine and acetylcholine when compared to those obtained at the same ILP in the presence of U46619. This inhibitory effect of muscarinic agonists on sympathetic nerve-induced responses was concentration-dependent. 4 Exogenously applied noradrenaline opposed the contractile effect of U46619 and acetylcholine to a similar extent, indicating that a comparable degree of postjunctional functional antagonism exists between the sympathetic neurotransmitter noradrenaline and both spasmogens. 5 The selective M2 muscarinic antagonists, gallamine and methoctramine, altered neither the postjunctional contractile action of acetylcholine nor its inhibitory effect on sympathetic nerve-induced relaxations. In addition, the inhibitory effect of acetylcholine was not modified by concentrations of pirenzepine known to block M1 muscarinic receptors. 6 The postjunctional contractile action of acetylcholine and its inhibitory effect on sympathetic neuro-transmission were antagonized by atropine, by the M3 muscarinic antagonist hexahydrosiladiphenidol and by higher concentration of pirenzepine. 7. These results suggest that in the guinea-pig trachea, muscarinic cholinoreceptor agonists inhibit sympathetic neurotransmission via activation of muscarinic receptors located on the sympathetic nerve endings. These inhibitory prejunctional muscarinic heteroreceptors are of the M3 subtype.

Clinical dysautonomia in patients with bronchial asthma. Study with seven autonomic function tests

Fifty asthmatic patients and 20 healthy control subjects, carefully age- and sex-matched, were subjected to seven standardized tests to evaluate their autonomic status. Due care was taken to remove factors which could interfere with results. Of the tests concerned with the parasympathetic system, the intravenous atropine test (p greater than 0.10) and heart rate response to standing (p greater than 0.01) which measured the basal parasympathetic tone, did not show a significant difference. Tests requiring stimulation of the parasympathetic system, ie, deep breathing test (p less than 0.001), Valsalva maneuver (p less than 0.001), and carotid sinus massage (p less than 0.001) showed significantly heightened response. Postural fall of blood pressure (p greater than 0.10) and sustained hand grip test (p greater than 0.10), chiefly concerned with the sympathetic system, did not show a significant difference. Of the 50 asthmatic patients, nine were atopic and 41 nonatopic. When the results were compared in the two groups separately, we found that there was no alteration in the measurements except the intravenous atropine test which showed heightened response with atopic subjects (p less than 0.05). These results suggest that hyperresponsiveness of the parasympathetic system is an important factor in producing bronchial spasm in asthmatic patients, and atopic and nonatopic subjects do not differ much in their autonomic status.

Tracheal parasympathetic neurons of rat, mouse and guinea pig: partial expression of noradrenergic phenotype and lack of innervation from noradrenergic nerve fibres

Noradrenergic nerves were studied in whole-mount preparations of the rat, mouse and guinea pig trachea by means of glyoxylic acid-induced catecholamine fluorescence and dopamine beta-hydroxylase immunoreactivity. In an effort to raise tissue levels of catecholamines, some specimens were also treated with the monoamine oxidase inhibitor pargyline, and with L-DOPA, a precursor of noradrenaline. Noradrenergic nerve fibres were detected around blood vessels, within the tracheal smooth muscle and in the mucosa, but never around or in the proximity of neurons of the tracheal ganglia, even after amine precursor loading. These parasympathetic ganglion cells did not show catecholamine fluorescence under control conditions. In the rat and mouse, but not in the guinea pig, some tracheal neurones were dopamine beta-hydroxylase immunoreactive and showed uptake and metabolism of amine precursors, thus expressing aspects of the catecholaminergic phenotype.

Effect of pirenzepine and gallamine on cardiac and pulmonary muscarinic receptors in the rabbit

1. The effect of muscarinic antagonists considered to be selective for M1 receptors (pirenzepine) and for M2 receptors (gallamine) were studied on bronchoconstriction and bradycardia elicited by stimulation of the vagal nerves and by i.v. acetylcholine (ACh) in anaesthetized rabbits. 2. Pirenzepine was equipotent as an antagonist of ACh-induced responses at postjunctional muscarinic receptors in the heart, lung and blood vessels, whereas gallamine was at least ten times less potent at pulmonary and vascular muscarinic receptors. Thus, gallamine never caused complete inhibition of bronchoconstrictor or hypotensive responses to i.v. ACh, whereas doses of pirenzepine in excess of 1 mumol kg-1 abolished all muscarinic responses. 3. In the lung, both antagonists inhibited bronchoconstriction caused by vagal stimulation and ACh-induced bronchoconstriction to the same extent (pirenzepine, mean ED50 65 +/- 22 and, 130 +/- 28 nmol kg-1 respectively; gallamine, ED50 greater than 10,000 nmol kg-1 for both responses). Enhancement of vagally-induced bronchoconstriction was never observed. 4. In the heart, however, both pirenzepine and gallamine were ten times less potent as antagonists of vagally-induced bradycardia than of ACh-induced bradycardia. This differential blockade was unaltered by propranolol (1 mg kg-1) pretreatment. 5. It is concluded that there is no evidence for M1 or M2 muscarinic receptors in the pulmonary innervation of the rabbit and the potency of the antagonists in abolishing in abolishing vagally-induced bronchoconstriction was consistent with blockade of M3 muscarinic receptors on airway smooth muscle. 6. The results suggest that M2 muscarinic receptors may exert an inhibitory effect on transmission in the parasympathetic nerves innervating the heart in the rabbit. Blockade of such neuronal receptors would increase transmitter output to the atrial cells and explain the low potency of both antagonists in abolishing vagally-induced bradycardia in the rabbit.

Regulation of bronchomotor tone in conscious calves

The purpose of this study was to investigate the effects of some alpha and beta sympathomimetic and sympatholytic drugs on respiratory impedance in healthy conscious calves. Ten Friesian calves were investigated in this study. The forced oscillation technique was used to measure the resistance (Rrs) and the reactance (Xrs) of the respiratory system at frequencies ranging from 4 to 26 Hz. Isoprenaline (1 microgram/kg i.v.), propranolol (3 micrograms/kg i.v.), noradrenaline (2 micrograms/kg i.v.), xylazine (20 micrograms/kg i.v.) and yohimbine (0.25 mg/kg i.v.) were were administered. Isoprenaline induced a significant decrease of Rrs. An increase of Rrs after administration of propranolol was observed but without any change of the frequency dependence of Rrs. A small increase in the resonant frequency was also recorded. A decrease of Rrs was recorded after yohimbine injection. Noradrenaline and xylazine administration increased the resistances and the resonant frequency and induced a negative frequency dependence of Rrs. These results suggest that (1) the major effects of beta adrenergic drugs are on the central airways, (2) the alpha adrenergic system may play a role on the regulation of bronchomotor tone in calves, (3) the effects of alpha adrenergic drugs are on both central and peripheral airways and (4) the forced oscillation technique allows the differentiation of calibre changes occurring in small and large airways.

Effects of xylazine and acepromazine on bronchomotor tone of anaesthetised ponies

The effects of xylazine (an alpha 2-adrenoceptor agonist) and acepromazine (an alpha-adrenoceptor antagonist) on bronchomotor tone were investigated in seven anaesthetised, apnoeic ponies using a computer aided forced oscillation technique, which separates changes in bronchial calibre from changes in lung volume. Both agents produced bronchodilatation and a decrease in lung volume.

Autoradiographic visualization of muscarinic receptors in pulmonary nerves and ganglia

We investigated autoradiographically the distribution of muscarinic receptors in bovine airways using (-)-[3H]quinuclidinyl benzilate as radioligand. The autoradiographs demonstrated the presence of muscarinic receptors in smooth muscle as well as neuronal muscarinic receptors in pulmonary nerves and ganglia. It is reasonable to believe that the neuronal muscarinic receptors participate in the regulation of neurotransmitter release at the peripheral nerve terminals innervating the bronchial smooth muscle.

The effects of alpha 2 adrenoceptor agonists on airway pressure in anaesthetized sheep

Xylazine and clonidine, given intravenously, cause an increase in airway pressure in the anaesthetized, ventilated sheep. This increase was dose dependent and was not mediated by histamine, nor was it blocked by the alpha 1-adrenoceptor antagonist prazosin. However, the increase was abolished by the alpha 2-adrenoceptor antagonist, idazoxan. When the alpha 2-adrenoceptor agonists were administered into the cerebrospinal fluid by injection into the cisterna magna there was no increase in airway pressure, although a similar dose given peripherally still produced an effect. These findings would indicate that the increase in airway pressure seen in these sheep, following administration of xylazine and clonidine, was mediated by peripherally located alpha 2-adrenoceptors.

Structure, function, and metabolism in the lung

Research into the molecular basis of cellular injury and repair will lead to advances in our understanding of the pathogenesis of infectious and noninfectious respiratory disease in cattle. In order to appreciate these advances fully, it is necessary to define the basics of structure, function, and metabolism in the respiratory system.

A light and fluorescence cytochemical and electron microscopic study of granule-containing cells in the intrapulmonary ganglia of Pseudemys scripta elegans

In the lung of the red-eared turtle, large numbers of intramural ganglia located in the intraparenchymal connective tissue are demonstrated. Numerous cells in close proximity to the principal ganglionic neurons displayed a bright blue-white formaldehyde-induced fluorescence. Microspectrofluorometric analysis revealed the presence of dopamine (DA) in all cells measured. Subsequent light histochemical staining of the fluorescent sections showed the DA-containing cells to display argentaffinity. Electron microscopy of serial sections revealed cells characterized by dense-cored vesicles corresponding to the intensely formaldehyde-induced fluorescent cells. The argentaffin technique performed directly on ultrathin sections selectively stained the dense-cored vesicles. After fixation with glutaraldehyde followed by dichromate, x-ray microanalysis showed the chromium to be incorporated into the dense granules. Cholinergic-type nerve endings formed axosomatic synaptic contacts with the DA-containing cells, which can therefore be considered as intrinsic postganglionic elements. No efferent synapses from the granule-containing cells to the principal ganglionic neurons could be observed. The granule-containing cells occurred solitarily and in clusters, partially invested with satellite cells, and usually located near fenestrated capillaries; they displayed cytoplasmic processes and indicated emiocytotic granule release. Adjacent granule-containing cells were separated by spaces about 20 nm wide, gradually widening to form intercellular channels with apically projecting microvilli and primary cilia. It is concluded that the intrapulmonary granule-containing cells of the red-eared turtle belong to the APUD system. Furthermore, morphologically these cells appeared to possess a special sensory apparatus which designates them as paraneurons. The possible physiological significance of these intrapulmonary granule-containing cells is discussed.

Recurrence of asthma following removal of a noradrenaline-secreting phaeochromocytoma

A patient with asthma and a phaeochromocytoma is described. At about the time she was first noted to be hypertensive her asthma resolved spontaneously but bronchospasm returned with some severity when the tumour was removed. The phaeochromocytoma was of the noradrenaline secreting variety. Possible mechanisms through which this catecholamine might have produced the observed alleviation of asthma are considered.

Modulation of bronchoconstrictor responses to histamine in pithed guinea-pigs by sympathetic nerve stimulation

1 Electrical stimulation (40V, 0.5-8 Hz, pulse width 0.5 ms) of the thoracic spinal outflow for between 10 and 120 s inhibited histamine-induced bronchoconstriction in pithed guinea-pigs. 2 The degree of this bronchodilatation varied with the position of the stimulating electrode within the spinal canal. Two maxima were identified. The first, at the level of the 9th and 10th thoracic vertebrae, was abolished by adrenalectomy. The second, at the level of the 3rd and 4th thoracic vertebrae, was associated with tachycardia and was unchanged by adrenalectomy. 3 The magnitude of this second bronchodilator effect varied with the frequency of stimulation. It was abolished by pretreatment with reserpine (5 mg/kg i.p. 48 and 24 h beforehand) and was competitively blocked by propranolol (0.01-1.0 mg/kg). 4 These observations are consistent with the view that bronchodilator tone is derived from neuronally-released noradrenaline within the lung. The noradrenaline probably overflows from well-innervated vasculature adjacent to sparsely innervated airways.

Distribution of pulmonary cholinergic nerves in the rabbit

Investigations of the nerves of the rabbit lung, by light and electron microscopy, showed a dense acetylcholinesterase-positive innervation of the bronchi through the bronchiolar level. Large nerve bundles were found to decrease in size as they progressed from extrachondral to subchondral connective tissue, forming complex networks of mostly terminal fibres in the muscle layer. In several instances single fibres penetrated the submucosal layer and approached the mucosa. Gangliocytes, which also reacted positively for cholinesterase, were visible in the vicinity of the large peribronchial bundles. Gangliocytes rarely were seen in association with the vasculature. Blood vessels received a much less dense cholinesterase-positive nerve supply than the bronchi. Single, non-terminal fibres were noted at the adventitiomedial junction of the pulmonary artery and vein. In addition, segments of nerve fibres (networks) were observed in the arterial and venous smooth muscle layers. Cholinesterase-positive innervation was even less extensive in the veins than in the arteries.

Catecholamine transport in isolated lung parenchyma of pig

1 Lung parenchyma strips of the pig incubated at 37 degrees C with [(3)H]-(-)-noradrenaline ([(3)H]-NA) or [(3)H]-(+/-)-isoprenaline ([(3)H]-Iso), accumulated radioactivity via saturable, high affinity uptake processes. Apparent saturation constants (K(m)) for [(3)H]-NA and [(3)H]-Iso were 1.34 x 10(-6) M and 1.63 x 10(-6) M respectively, while apparent transport maxima (V(max)) were 4.86 and 1.63 x 10(-9) mol min(-1) g(-1) respectively.2 Cellular accumulation of radioactivity from radiolabelled catecholamines was greatly reduced by lowering the temperature to 7 degrees C, pretreatment with ouabain (100 muM), phentolamine (15 muM) or phenoxybenzamine (80 muM). However, accumulation of radioactivity derived from ((3)H]-NA was inhibited selectively by cocaine (10 muM) and desipramine (1 muM), while normetanephrine (80 muM) and 3-O-methylisoprenaline (50 muM) caused much greater reductions in cellular radioactivity from [(3)H]-Iso than from ((3)H]-NA. Taken together with information from kinetic studies, the results indicate that these amines are transported by separate uptake processes.3 Cocaine (50 muM) which selectively reduced [(3)H]-NA transport, had no significant effect on the sensitivity (EC(50)) of isolated parenchyma lung strips of the pig to the contractile effects of cumulative concentrations of NA. The catechol-O-methyl transferase (COMT) inhibitor, U-0521 (60 muM), also failed to alter the potency of NA, while normetanephrine (80 muM) caused a 2 fold decrease in potency.4 Phentolamine (15 muM), which reduced the cellular accumulation of radioactivity derived from [(3)H]-Iso by 64%, caused a small potentiation of Iso-induced relaxations of porcine lung strips. Normetanephrine (80 muM) and 3-O-methylisoprenaline (50 muM), which also depressed the accumulation of cellular radioactivity from [(3)H]-Iso by > 50%, caused rightward shifts in Iso concentration-effect curves as a result of beta-adrenoceptor blockade. In sharp contrast, cortisol (80 muM) and U-0521 (60 muM), which caused smaller reductions in the cellular accumulation of radioactivity derived from [(3)H]-Iso, both caused an approximately 9 fold potentiation of responses to Iso in isolated lung strips.5 The results indicate that the major sites of uptake and metabolism of NA in porcine parenchyma strip are remote from alpha-adrenoceptors mediating NA-induced contraction. Similarly, some major sites of uptake of Iso are remote from beta-adrenoceptors mediating Iso-induced relaxation. However, beta-adrenoceptors are apparently in close proximity to a compartment containing COMT activity.

Adrenergic and non-adrenergic inhibitory nerves in mammalian airways

A study of the actions of adrenergic and non-adrenergic nerves which affect mammalian airways was carried out. The preparations studied included strips of lung from guinea-pig, rat, rabbit, monkey and human, tracheal strips from the first 4 animals and bronchial strips from the last 3. Relaxations to field stimulation of sympathetic nerves were found in the guinea-pig trachea only. Functional nonadrenergic inhibitory nerves were found in the larger airways of all species except rat. Lung strips from all the mammals failed to respond to sympathetic or nonadrenergic inhibitory nerve stimulation suggesting a lack of functional inhibitory nerves of either type in the fine airways. Studies on the distribution of adrenergic nerves showed that primary target of the nerves in all species appeared to be the vasculature, especially in lung. Occasional fibres were seen entering the smooth muscle of the fine airways in guinea-pig, rabbit, and rat, but not in monkey or human lung or in monkey trachea or bronchus or human bronchus. Guinea-pig and rabbit trachealis muscles received a significant innervation but only the guinea-pig tissue responded to sympathetic stimulation. Inhibitory beta-adrenoceptors were demonstrated in the proximal airways of all species except rabbit. The fine airways of rat, monkey and human contained a mixed population of alpha-excitatory and beta-inhibitory adrenoceptors only were found in guinea-pig lung and alpha-adrenoceptors only in rabbit lung.

Catecholamine- and acetylcholinesterase-containing nerves in human lower respiratory tract

The innervation of human lower respiratory tract was studied with special emphasis on airways with sodium-potassium glyoxylic acid (SPG) and acetylcholinesterase (AChE) methods to demonstrate catecholamine-containing and acetylcholinesterase-containing nerve fibers. AChE-method revealed a rich network of cholinesterase positive nerves both inside the bronchial glands where they run around and between the acini, and the airway smooth muscle from secondary bronchi to terminal bronchioli. No AChE-positive fibers were found in connection with the blood vessels or within the epithelium of bronchi or bonchioli. The AChE-positive nerve fibers in bronchial smooth muscle greatly outnumbered those containing catecholamine. The SPG-method revealed the presence of adrenergic nerves from the level of secondary bronchi to that of terminal bronchioli. These nerve fibers were most abundant in bronchial glands, where their amount was equal and distribution similar to those of AChE-containing nerve fibers. Outside the glands adrenergic fibers were constantly seen in connection with the bronchial blood vessels in connective tissues surrounding bronchi. A few nerve fibers were also present in airway smooth muscle from the secondary bronchi to terminal bronchioli.

Pulmonary mechanics during hypoxia in spontaneously breathing anesthetized rabbits

Changes in lung mechanics were measured during hypoxia (FIO2 = 0.10 during 5 min) in spontaneously breathing anesthetized rabbits. In intact animals, hypoxia induced scattered variations in total lung resistance (RL) (decrease, increase or no alteration) and dynamic lung compliance (CL), whereas in carotid body denervated animals it was accompanied by an almost constant decrease in RL (-12%); but if a subsequent vagotomy was performed, there was no significant variation in RL. In animals which had been only vagotomized, CL decreased significantly during hypoxia (-23%) without any associated change in RL. So, the arterial chemoreceptor mediated bronchoconstrictor effects due to hypoxia could be normally masked by the dilator effects (metabolic and/or sympathetic) on the airways.

Immunologic and neuropharmacologic stimulation of mucous glycoprotein release from human airways in vitro

Human bronchial airways obtained after surgical resection were maintained in tissue culture for 24-48 h. Incorporation of [(3)H]- or [(14)C]-glucosamine, [(14)C]threonine, or Na(2)[(35)S]O(4) to the culture media resulted in biosynthesis of two radiolabeled glycoproteins-one filtering in the exclusion volume of Sepharose 2B, and the other filtering with an approximate molecular weight of 400,000. Both fractions had similar elution patterns from DEAE-cellulose anion exchange chromatography. [(3)H]Glucosamine was incorporated equally into the two fractions. The effects of anaphylaxis, histamine, and several neurohormones upon the release of [(3)H]glucosamine-labeled glycoproteins were analyzed, making no attempt to separate the two glycoprotein fractions. Three lines of evidence were found suggesting that mast-cell degranulation increases mucous release from cultured airways. (a) Supernatant fluids from anaphylaxed peripheral human lung that contained 200-400 ng/ml histamine and 400-1,000 U/ml slow-reacting substance of anaphylaxis (SRS-A) increased release by 40+/-18%. (b) The addition of antigen to IgE-sensitized airways led to the release of 26+/-7% of the total histamine and a 36+/-14% increase in mucous release. (c) Reversed anaphylaxis with anti-IgE antibodies induced a 36+/-6% release of histamine from the airways and an increase in the release of mucous glycoproteins of 25+/-9%. Exogenous histamine added to airways increased mucous glycoprotein release, an effect prevented by cimetidine, an H-2 antagonist. Selective histamine H-2, but not H-1 agonists increased mucous glycoprotein release, suggesting the possibility that anaphylaxis of airways results in increased mucous glycoprotein release partly through histamine H-2 stimulation.A cholinomimetic agonist, methacholine, increased mucous release; this response was prevented by atropine which alone had no effect. No response to beta-adrenergic stimulation with either isoproterenol or epinephrine was noted. However, alpha-adrenergic stimulation with either norepinephrine combined with propranolol or phenylephrine alone resulted in dose-related increases in glycoprotein release. Both alpha-adrenergic and cholinergic stimulation of human tissues induce the formation of guanosine 3',5'-phosphoric acid (cyclic GMP), and 8-bromo cyclic GMP added to the airways led to increased mucous secretion. Thus, it seems likely that neurohormones capable of stimulating cyclic GMP formation in human airways may lead to increased mucous glycoprotein release.

Innervation of rabbit fetal lungs

Nerve fibers, autonomic ganglia, and neuroepithelial bodies of the lungs of rabbit fetuses, 17 to 31 days gestational age, were studied with neurohistological techniques including silver impregnation, acetylcholinesterase histochemistry, and glyoxylic-acid-induced histofluorescence for monoamines. The silver impregnation method showed that nerve fibers and ganglia accompanied the bronchi and large pulmonary blood vessels to enter the developing lungs by the 17th day of gestation. Cholinergic and adrenergic nerves began to appear in the walls of the bronchi on the 21st day. The developing pulmonary arteries had accompanying adrenergic nerves on the 25th day. Acetylcholinesterase-positive parasympathetic ganglia were seen on the 27th day. Silver-impregnated nerve fibers in the developing alveolar walls and pleura were found on the 25th day. Neuroepithelial bodies and specialized single cells which were argyrophilic, acetylcholinesterase-positive, and fluorescent could be demonstrated in 19--21-day-old and older fetuses; and some of these structures were innervated by sensory and autonomic motor fibers. These observations indicated that nervous tissue and neuroepithelial bodies appeared in the lungs during the glandular stage of the lung development and that differentiation of adrenergic and cholinergic nerves began in the late glandular stage.

A morphometric analysis of the autonomic innervation of cat tracheal glands

Quantitative methods have been used to examine the distribution of adrenergic and cholinergic axon varicosities to serous and mucous cells of cat tracheal glands. Cats were injected with 5-hydroxydopamine (5-OHDA) prior to removal of the trachea in order to fill adrenergic vesicles with intensely osmiophilic material. This facilitated the identification of adrenergic varicosities and provided a means by which they could be easily discriminated from cholinergic varicosities. Of all varicosities identified within 10 micrometer of the glands, 90% were cholinergic and 10% were adrenergic. Most of these varicosities were present in interstitial bundles located between acini. A small number of cholinergic varicosities, however, were located within 20 nm of acinar cells, forming close contact junctions. No differential innervation of serous and mucous cells was observed.

Alpha-adrenergic hyper-responsiveness in asthma

Because alpha-adrenergic stimulation causes bronchoconstriction, the alpha-adrenergic responsiveness of 21 subjects with allergic asthma was compared with that of 16 subjects with allergic rhinitis and 38 normal control subjects. None of the patients had taken medications for at least 30 days before study. Alpha-adrenergic responsiveness was measured by the capacity of phenylephrine to constrict the cutaneous vascular bed and to dilate the pupillary sphincter muscle. Asthmatic subjects required 4.0 +/- 0.6 ng to reduce their cutaneous blood flow by 50 per cent, whereas normal controls required 32.0 +/- 7.5 ng (P less than 0.005) and subjects with allergic rhinitis required 23.7 +/- 9.4 ng (P less than 0.02). The pupils of asthmatic subjects dilated by greater than 0.5 mm in response to 1.8 +/- 0.14 per cent phenylephrine, patients with allergic rhinitis required 2.4 +/- 0.16 (P less than 0.01), and normal controls needed 2.7 +/- 0.07 (P less than 0.00001). Therefore, the patients with allergic asthma had significantly enhanced alpha-adrenergic responses when compared both to normal subjects and patients with allergic rhinitis; the possibility that increased alpha-adrenergic activity contributes to the asthmatic diathesis warrants further exploration.

Occurrence and distribution of VIP nerves in the nasal mucosa and tracheobronchial wall

Nerves displaying vasoactive intestinal peptide (VIP) immunoreactivity were detected in the upper respiratory tract of guinea pigs, rabbits and cats. VIP nerves were numerous in the cat, less numerous in the rabbit and rare in the guinea pig. In the nasal mucosa, fine varicose VIP nerves were found to surround nasal glands and small blood vessels. In the tracheobronchial wall VIP nerves were observed around seromucous glands, blood vessels and smooth muscle. Ganglia located in the walls of the trachea and main bronchi contained clusters of VIP immunoreactive nerve cell bodies, conceivably representing the origin of the VIP fibres found in this region.

Tne density of adrenergic nerves at various levels in the guinea-pig lung

1. Gunea-pig tracheal and lung segments were systematically examined for adrenergic nerves using the fluorescence histochemical technique. Fluorescence in nerves was enhanced with alpha-methylnoradrenaline or by pretreating animals with nialamide. 2. There was a progressive decrese in density of fluorescent fibres in airway smooth muscle from the laryngeal end of the trachea, which was densely innervated, to the bronchioles, which contained only occasional fibres. This was despite obvious fluorescence in blood vessels in the lung. 3. It is suggested that, if adrenergic nerves are involved in reflex bronchodilatation in this species, they directly control larger airways and other factors, e.g. non-adrenergic inhibitory nerves, may be important in the control of smaller airways.

Toluene diisocyanate pulmonary disease: immunopharmacologic and mecholyl challenge studies

Selected workers exhibiting clinical "sensitivity" to toluene diiosocyanate (TDI) (wheezing, cough, and dyspnea upon entering a TDI-containing area) were studied for : (1) in vitro TDI-induced leukocyte histamine release; (2) determination of cyclic 3',5' adenosine monophosphate (cAMP) levels of lymphocytes exposed to TDI; (3) effect of TDI on the isoproterenol-induced increase of lymphocyte cAMP levels: and (4) acetyl-beta-methylcholine (mecholyl) inhalation challenge. TDI did not induce histamine release from leukocytes of "sensitive" or "nonsensitive" individuals, nor were lymphocyte cAMP levels affected by in vitro TDI exposure, TDI did, however, diminish in vitro stimulation of cAMP by isoproterenol. This effect, seen with cells of "sensitive" and "nonsensitive" individuals, appeared to be dose-dependent; there were no significant differences between the two groups. When challenged with mecholyl, 7 of 10 "sensitive" but only 1 of 10 "nonsensitive" individuals showed a greater than 20% decrease in FEV1. These results suggest that TDI-induced obstructive airways disorders may be associated with altered beta-adrenergic function.