Chemical profile of vagal preganglionic motor cells innervating the airways in ferrets: the absence of noncholinergic neurons

2004 ◽  
Vol 97 (4) ◽  
pp. 1508-1517 ◽  
Author(s):  
Prabha Kc ◽  
Catherine A. Mayer ◽  
Musa A. Haxhiu
Keyword(s):  
Smooth Muscle ◽  
Muscarinic Receptor ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Smooth Muscle Relaxation ◽  
Receptor Blockade ◽  
Double Labeling ◽  
Smooth Muscle Tone ◽  
Preganglionic Neurons ◽  
Stimulation Of

In ferrets, we investigated the presence of choline acetyltransferase (ChAT), vasoactive intestinal peptide (VIP), and markers for nitric oxide synthase (NOS) in preganglionic parasympathetic neurons innervating extrathoracic trachea and intrapulmonary airways. Cholera toxin β-subunit, a retrograde axonal transganglionic tracer, was used to identify airway-related vagal preganglionic neurons. Double-labeling immunohistochemistry and confocal microscopy were employed to characterize the chemical nature of identified airway-related vagal preganglionic neurons at a single cell level. Physiological experiments were performed to determine whether activation of the VIP and ChAT coexpressing vagal preganglionic neurons plays a role in relaxation of precontracted airway smooth muscle tone after muscarinic receptor blockade. The results showed that 1) all identified vagal preganglionic neurons innervating extrathoracic and intrapulmonary airways are acetylcholine-producing cells, 2) cholinergic neurons innervating the airways coexpress ChAT and VIP but do not contain NOS, and 3) chemical stimulation of the rostral nucleus ambiguus had no significant effect on precontracted airway smooth muscle tone after muscarinic receptor blockade. These studies indicate that vagal preganglionic neurons are cholinergic in nature and coexpress VIP but do not contain NOS; their stimulation increases cholinergic outflow, without activation of inhibitory nonadrenergic, noncholinergic ganglionic neurons, stimulation of which induces airway smooth muscle relaxation. Furthermore, these studies do not support the possibility of direct inhibitory innervation of airway smooth muscle by vagal preganglionic fibers that contain VIP.

Catecholaminergic microcircuitry controlling the output of airway-related vagal preganglionic neurons

2003 ◽  
Vol 94 (5) ◽  
pp. 1999-2009 ◽  
Author(s):  
Musa A. Haxhiu ◽  
Prabha Kc ◽  
Burim Neziri ◽  
Bryan K. Yamamoto ◽  
Donald G. Ferguson ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Muscle Relaxation ◽  
Smooth Muscle Relaxation ◽  
Cell Group ◽  
Norepinephrine Release ◽  
Smooth Muscle Tone ◽  
Preganglionic Neurons ◽  
Stimulation Of

In this study, we have investigated the ultrastructure and function of the catecholaminergic circuitry modulating the output of airway-related vagal preganglionic neurons (AVPNs) in ferrets. Immunoelectron microscopy was employed to characterize the nature of catecholaminergic innervation of AVPN at the ultrastructural level. In addition, immunofluorescence was used to examine the expression of the α2A-adrenergic receptor (α2A-AR) on AVPNs, and norepinephrine release within the rostral nucleus ambiguous (rNA) was measured by using microdialysis. Physiological experiments were performed to determine the effects of stimulation of the noradrenergic locus coeruleus (LC) cell group on airway smooth muscle tone. The results showed that 1) catecholaminergic nerve endings terminate in the vicinity of identified AVPNs but very rarely form axosomatic or axodendritic synapses with the AVPNs that innervate the extrathoracic trachea; 2) AVPNs express the α2A-AR; 3) LC stimulation-induced norepinephrine release within the rNA region was associated with airway smooth muscle relaxation; and 4) blockade of α2A-AR on AVPNs diminished the inhibitory effects of LC stimulation on airway smooth muscle tone. It is concluded that a noradrenergic circuit originating within the LC is involved in the regulation of AVPN activity within the rNA, and stimulation of the LC dilates the airways by the release of norepinephrine and activation of α2A-AR expressed by AVPNs, mainly via volume transmission.

S-nitrosoglutathione breakdown prevents airway smooth muscle relaxation in the guinea pig

2000 ◽  
Vol 279 (4) ◽  
pp. L716-L721 ◽  
Author(s):  
Kezhong Fang ◽  
Roger Johns ◽  
Timothy Macdonald ◽  
Michael Kinter ◽  
Benjamin Gaston
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Muscle Relaxation ◽  
Tracheal Ring ◽  
Protein Fractions ◽  
Smooth Muscle Relaxation ◽  
Smooth Muscle Tone ◽  
Catabolic Activity

Airway levels of the endogenous bronchodilator S-nitrosoglutathione (GSNO) are low in children with near-fatal asthma. We hypothesized that GSNO could be broken down in the lung and that this catabolism could inhibit airway smooth muscle relaxation. In our experiments, GSNO was broken down by guinea pig lung homogenates, particularly after ovalbumin sensitization (OS). Two lung protein fractions had catabolic activity. One was NADPH dependent and was more active after OS. The other was NADPH independent and was partially inhibited by aurothioglucose. Guinea pig lung tissue protein fractions with GSNO catabolic activity inhibited GSNO-mediated guinea pig tracheal ring relaxation. The relaxant effect of GSNO was partially restored by aurothioglucose. These observations suggest that catabolism of GSNO in the guinea pig 1) is mediated by lung proteins, 2) is partially upregulated after OS, and 3) may contribute to increased airway smooth muscle tone. We speculate that enzymatic breakdown of GSNO in the lung could contribute to asthma pathophysiology by inhibiting the beneficial effects of GSNO, including its effect on airway smooth muscle tone.

Activation of the midbrain periaqueductal gray induces airway smooth muscle relaxation

2002 ◽  
Vol 93 (2) ◽  
pp. 440-449 ◽  
Author(s):  
Musa A. Haxhiu ◽  
Bryan K. Yamamoto ◽  
Ismail A. Dreshaj ◽  
Donald G. Ferguson
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Muscle Relaxation ◽  
Gaba Release ◽  
Periaqueductal Gray ◽  
Nucleus Ambiguus ◽  
Smooth Muscle Relaxation ◽  
Receptor Subtype ◽  
Smooth Muscle Tone

In this study, we examined effects of chemical stimulation of the ventrolateral region of the midbrain periaqueductal gray (vl PAG) on airway smooth muscle tone. We observed that in anesthetized, paralyzed, and artificially ventilated ferrets, vl PAG stimulation elicited airway smooth muscle relaxation. To clarify the mechanisms underlying this observation, we examined the GABA-GABAA receptor signaling pathway by 1) examining the expression of GABAA receptors on airway-related vagal preganglionic neurons (AVPNs) located in the rostral nucleus ambiguus region (rNA), by use of receptor immunochemistry and confocal microscopy; 2) measuring GABA release within the rNA by using microdialysis; and 3) performing physiological experiments to determine the effects of selective blockade of GABAA receptors expressed by AVPNs in the rNA region on vl PAG-induced airway relaxation, thereby defining the role of the GABAA receptor subtype in this process. We observed that AVPNs located in the rNA region do express the GABAA receptor β-subtype. In addition, we demonstrated that activation of vl PAG induced GABA release within the rNA region, and this release was associated with airway smooth muscle relaxation. Blockade of the GABAA receptor subtype expressed by AVPNs in the rNA by bicuculline diminished the inhibitory effects of vl PAG stimulation on airway smooth muscle tone. These data indicate, for the first time, that activation of vl PAG dilates the airways by a release of GABA and activation of GABAA receptors expressed by AVPNs.

EETs relax airway smooth muscle via an EpDHF effect: BKCa channel activation and hyperpolarization

2001 ◽  
Vol 280 (5) ◽  
pp. L965-L973 ◽  
Author(s):  
Catherine Benoit ◽  
Barbara Renaudon ◽  
Dany Salvail ◽  
Eric Rousseau
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Molecular Mechanisms ◽  
Muscle Tone ◽  
Muscle Relaxation ◽  
Smooth Muscle Relaxation ◽  
Epoxyeicosatrienoic Acids ◽  
Bkca Channel ◽  
Channel Activity ◽  
Cytochrome P 450

Epoxyeicosatrienoic acids (EETs) are produced from arachidonic acid via the cytochrome P-450 epoxygenase pathway. EETs are able to modulate smooth muscle tone by increasing K+ conductance, hence generating hyperpolarization of the tissues. However, the molecular mechanisms by which EETs induce smooth muscle relaxation are not fully understood. In the present study, the effects of EETs on airway smooth muscle (ASM) were investigated using three electrophysiological techniques. 8,9-EET and 14,15-EET induced concentration-dependent relaxations of the ASM precontracted with a muscarinc agonist (carbamylcholine chloride), and these relaxations were partly inhibited by 10 nM iberiotoxin (IbTX), a specific large-conductance Ca2+-activated K+ (BKCa) channel blocker. Moreover, 3 μM 8,9- or 14,15-EET induced hyperpolarizations of −12 ± 3.5 and −16 ± 3 mV, with EC50 values of 0.13 and 0.14 μM, respectively, which were either reversed or blocked on addition of 10 nM IbTX. These results indicate that BKCa channels are involved in hyperpolarization and participate in the relaxation of ASM. In addition, complementary experiments demonstrated that 8,9- and 14,15-EET activate reconstituted BKCa channels at low free Ca2+ concentrations without affecting their unitary conductance. These increases in channel activity were IbTX sensitive and correlated well with the IbTX-sensitive hyperpolarization and relaxation of ASM. Together these results support the view that, in ASM, the EETs act through an epithelium-derived hyperpolarizing factorlike effect.

A GABAergic inhibitory microcircuit controlling cholinergic outflow to the airways

2004 ◽  
Vol 96 (1) ◽  
pp. 260-270 ◽  
Author(s):  
Constance T. Moore ◽  
Christopher G. Wilson ◽  
Catherine A. Mayer ◽  
Sandra S. Acquah ◽  
V. John Massari ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Structural Characteristics ◽  
Nucleus Ambiguus ◽  
Acid Decarboxylase ◽  
Electron Microscopic ◽  
Synaptic Contacts ◽  
Smooth Muscle Tone ◽  
Rostral Nucleus

GABA is the main inhibitory neurotransmitter that participates in the regulation of cholinergic outflow to the airways. We have tested the hypothesis that a monosynaptic GABAergic circuit modulates the output of airway-related vagal preganglionic neurons (AVPNs) in the rostral nucleus ambiguus by using a dual-labeling electron microscopic method combining immunocytochemistry for glutamic acid decarboxylase (GAD) with retrograde tracing from the trachea. We also determined the effects of blockade of GABAA receptors on airway smooth muscle tone. The results showed that retrogradely labeled AVPNs received a significant GAD-immunoreactive (GAD-IR) terminal input. Out of a pooled total of 3,161 synaptic contacts with retrogradely labeled somatic and dendritic profiles, 20.2% were GAD-IR. GAD-IR terminals formed significantly more axosomatic synapses than axodendritic synapses ( P < 0.02). A dense population of GABAergic synaptic contacts on AVPNs provides a morphological basis for potent physiological effects of GABA on the excitability of AVPNs. GAD-IR terminals formed exclusively symmetric synaptic specializations. GAD-IR terminals were significantly larger ( P < 0.05) in both length and width than unlabeled terminals synapsing on AVPNs. Therefore, the structural characteristics of certain nerve terminals may be closely correlated with their function. Pharmacological blockade of GABAA receptors within the rostral nucleus ambiguus increased activity of putative AVPNs and airway smooth muscle tone. We conclude that a tonically active monosynaptic GABAergic circuit utilizing symmetric synapses regulates the discharge of AVPNs.

Modulation of vascular tone by neutrophils: dependence on endothelial integrity

1989 ◽  
Vol 257 (4) ◽  
pp. H1315-H1320
Author(s):  
J. L. Mehta ◽  
D. L. Lawson ◽  
W. W. Nichols ◽  
P. Mehta
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Relaxant ◽  
Muscle Tone ◽  
Muscle Relaxation ◽  
Smooth Muscle Relaxation ◽  
Smooth Muscle Tone ◽  
High Concentrations ◽  
Vascular Smooth Muscle Tone ◽  
Smooth Muscle Relaxant

To determine the influence of polymorphonuclear leukocytes (PMNLs) on vascular smooth muscle tone, isolated human PMNLs (10(4)–10(7) cells/ml) were suspended in a tissue bath with precontracted rat aortic rings with or without endothelium. PMNLs in low concentrations (10(4) and 10(5) cells/ml) caused a mild contraction, and in higher concentrations (10(6) and 10(7) cells/ml) caused a modest relaxation of aortic rings with intact endothelium. In contrast, PMNLs caused a potent concentration-dependent relaxation of deendothelialized rings (P less than 0.01 compared with rings with intact endothelium). The PMNL-induced vascular smooth muscle relaxation was abolished by both hemoglobin and methylene blue and potentiated by both superoxide dismutase and captopril. Although suspension of PMNLs caused release of eicosanoids, thromboxane A2 and prostacyclin, from rings with intact endothelium, neither indomethacin nor the TxA2-endoperoxide receptor antagonist SQ 29548 modified the effects of PMNLs on vascular smooth muscle tone. These observations suggest that unstimulated PMNLs generate a smooth muscle relaxant, which has biological characteristics similar to the endothelium-derived relaxing factor. Since the activity of this PMNL-derived smooth muscle relaxant is more pronounced in deendothelialized vascular segments, it appears that endothelium provides a barrier against vasorelaxation by high concentrations of PMNLs.

Airway basement membrane perimeter in human airways is not a constant; potential implications for airway remodeling in asthma

2004 ◽  
Vol 97 (2) ◽  
pp. 556-563 ◽  
Author(s):  
Brent E. McParland ◽  
Peter D. Paré ◽  
Peter R. A. Johnson ◽  
Carol L. Armour ◽  
Judith L. Black
Keyword(s):  
Smooth Muscle ◽  
Basement Membrane ◽  
Airway Smooth Muscle ◽  
Muscle Tone ◽  
Airway Remodeling ◽  
Organ Bath ◽  
Smooth Muscle Tone ◽  
Asthmatic Patients ◽  
Constant Potential ◽  
Human Airways

Many studies that demonstrate an increase in airway smooth muscle in asthmatic patients rely on the assumption that bronchial internal perimeter ( Pi) or basement membrane perimeter ( Pbm) is a constant, i.e., not affected by fixation pressure or the degree of smooth muscle shortening. Because it is the basement membrane that has been purported to be the indistensible structure, this study examines the assumption that Pbm is not affected by fixation pressure. Pbm was determined for the same human airway segment ( n = 12) fixed at distending pressures of 0 cmH2O and 21 cmH2O in the absence of smooth muscle tone. Pbm for the segment fixed at 0 cmH2O was determined morphometrically, and the Pbm for the same segment, had the segment been fixed at 21 cmH2O, was predicted from knowing the luminal volume and length of the airway when distended to 21 cmH2O (organ bath-derived Pi). To ensure an accurate transformation of the organ bath-derived Pi value to a morphometry-derived Pbm value, had the segment been fixed at 21 cmH2O, the relationship between organ bath-derived Pi and morphometry-derived Pbm was determined for five different bronchial segments distended to 21 cmH2O and fixed at 21 cmH2O ( r2 = 0.99, P < 0.0001). Mean Pbm for bronchial segments fixed at 0 cmH2O was 9.4 ± 0.4 mm, whereas mean predicted Pbm, had the segments been fixed at 21 cmH2O, was 14.1 ± 0.5 mm ( P < 0.0001). This indicates that Pbm is not a constant when isolated airway segments without smooth muscle tone are fixed distended to 21 cmH2O. The implication of these results is that the increase in smooth muscle mass in asthma may have been overestimated in some previous studies. Therefore, further studies are required to examine the potential artifact using whole lungs with and without abolition of airway smooth muscle tone and/or inflation.

Basenji-greyhound dog: increased m2 muscarinic receptor expression in trachealis muscle

1995 ◽  
Vol 268 (6) ◽  
pp. L935-L940 ◽  
Author(s):  
C. W. Emala ◽  
A. Aryana ◽  
M. A. Levine ◽  
R. P. Yasuda ◽  
S. A. Satkus ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Adenylyl Cyclase ◽  
Muscarinic Receptor ◽  
Airway Smooth Muscle ◽  
Muscle Relaxation ◽  
Receptor Expression ◽  
Smooth Muscle Relaxation ◽  
Muscarinic Agonists ◽  
M2 Muscarinic Receptor ◽  
Muscarinic M2 Receptors

Airway smooth muscle from asthmatic humans and from the Basenji-greyhound dog (BG) dog is hyporesponsive to beta-adrenergic agonist stimulation. Because adenylyl cyclase is under dual regulation in airway smooth muscle, we compared muscarinic receptor-coupled inhibition of adenylyl cyclase in airway smooth muscle from BG and mongrel dogs. Inhibition of forskolin-stimulated adenylyl cyclase activity by the muscarinic M2 agonist oxotremorine was greater in airway smooth muscle membranes from BG compared with mongrel controls. Quantitative immunoprecipitation studies showed increased numbers of m2 but not m3 muscarinic receptors in the BG airway smooth muscle. The enhanced ability of muscarinic agonists to inhibit adenylyl cyclase in BG airway smooth muscle may be due to the greater numbers of muscarinic m2 receptors, which may account in part for impaired airway smooth muscle relaxation in the BG model of airway hyperresponsiveness.

Mechanism of internal anal sphincter smooth muscle relaxation by phorbol 12,13-dibutyrate

2001 ◽  
Vol 280 (6) ◽  
pp. G1341-G1350 ◽  
Author(s):  
Sushanta Chakder ◽  
D. N. K. Sarma ◽  
Satish Rattan
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Anal Sphincter ◽  
Internal Anal Sphincter ◽  
Inhibitory Action ◽  
Muscle Tone ◽  
Muscle Relaxation ◽  
Muscle Cells ◽  
Smooth Muscle Relaxation ◽  
Smooth Muscle Tone

We investigated the mechanism of the inhibitory action of phorbol 12,13-dibutyrate (PDBu), one of the typical protein kinase C (PKC) activators, in in vitro smooth muscle strips and in isolated smooth muscle cells of the opossum internal anal sphincter (IAS). The inhibitory action of PDBu on IAS smooth muscle (observed in the presence of guanethidine + atropine) was partly attenuated by tetrodotoxin, suggesting that a part of the inhibitory action of PDBu is via the nonadrenergic, noncholinergic neurons. A major part of the action of PDBu in IAS smooth muscle was, however, via its direct action at the smooth muscle cells, accompanied by a decrease in free intracellular Ca2+ concentration ([Ca2+]i) and inhibition of PKC translocation. PDBu-induced IAS smooth muscle relaxation was unaffected by agents that block Ca2+ mobilization and Na+-K+-ATPase. The PDBu-induced fall in basal IAS smooth muscle tone and [Ca2+]i resembled that induced by the Ca2+ channel blocker nifedipine and were reversed specifically by the Ca2+ channel activator BAY K 8644. We speculate that a major component of the relaxant action of PDBu in IAS smooth muscle is caused by the inhibition of Ca2+ influx and of PKC translocation to the membrane. The specific role of PKC downregulation and other factors in the phorbol ester-mediated fall in basal IAS smooth muscle tone remain to be determined.

G protein-coupled receptor kinase 5 regulates airway responses induced by muscarinic receptor activation

2004 ◽  
Vol 286 (2) ◽  
pp. L312-L319 ◽  
Author(s):  
J. K. L. Walker ◽  
R. R. Gainetdinov ◽  
D. S. Feldman ◽  
P. K. McFawn ◽  
M. G. Caron ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
G Protein ◽  
Muscarinic Receptor ◽  
Airway Smooth Muscle ◽  
Muscarinic Receptors ◽  
Muscle Relaxation ◽  
Receptor Activation ◽  
Smooth Muscle Relaxation ◽  
Airway Responses ◽  
G Protein Coupled

G protein-coupled receptors (GPCRs) transduce extracellular signals into intracellular events. The waning responsiveness of GPCRs in the face of persistent agonist stimulation, or desensitization, is a necessary event that ensures physiological homeostasis. GPCR kinases (GRKs) are important regulators of GPCR desensitization. GRK5, one member of the GRK family, desensitizes central M2 muscarinic receptors in mice. We questioned whether GRK5 might also be an important regulator of peripheral muscarinic receptor responsiveness in the cardiopulmonary system. Specifically, we wanted to determine the role of GRK5 in regulating muscarinic receptor-mediated control of airway smooth muscle tone or regulation of cholinergic-induced bradycardia. Tracheal pressure, heart rate, and tracheal smooth muscle tension were measured in mice having a targeted deletion of the GRK5 gene ( GRK5- /-) and littermate wild-type (WT) control mice. Both in vivo and in vitro results showed that the airway contractile response to a muscarinic receptor agonist was not different between GRK5- /- and WT mice. However, the relaxation component of bilateral vagal stimulation and the airway smooth muscle relaxation resulting from β2-adrenergic receptor activation were diminished in GRK5- /- mice. These data suggest that M2 muscarinic receptor-mediated opposition of airway smooth muscle relaxation is regulated by GRK5 and is, therefore, excessive in GRK5- /- mice. In addition, this study shows that GRK5 regulates pulmonary responses in a tissue- and receptor-specific manner but does not regulate peripheral cardiac muscarinic receptors. GRK5 regulation of airway responses may have implications in obstructive airway diseases such as asthma or chronic obstructive pulmonary disease.

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