Tetrodotoxin-resistant non-cholinergic neurogenic contraction evoked by capsaicinoids and piperine on the guinea-pig trachea

Contraction of the isolated tracheal strip to capsaicin was prevented by chronic denervation of the tissue. Tetrodotoxin, hyoscine and hexamethonium caused no inhibition of the response, suggesting that tetrodotoxin-resistant terminal portions of non-cholinergic nerves were activated in this way. There was a strong correlation between the pain-producing and tracheoconstrictor effects of piperine, pungent and non-pungent capsaicin congeners. Common site of action was evidenced by crossed tachyphylaxis. It is concluded that the capsaicin-sensitive sensory nerve endings have a dual sensory-efferent function. Excitation-secretion coupling in this system could operate without an axon reflex.     

Efferent innervation of the cervical segment of the trachea in early postnatal ontogenesis

A method based on retrograde axonal transport of horseradish peroxidase was used to study the efferent innervation of the cervical segment of the trachea in neonatal kittens and kittens aged 10, 20, and 30 days and two months. Labeled neurons in all animals were located in the cranial cervical, middle cervical, and cervicothoracic sympathetic ganglia on the right and left sides, at the level of the medulla oblongata, and in the dorsal and ambiguus nuclei of the vagus nerves. Up to age 30 days, neurons were also seen in the ventral horns of the spinal cord in segments C1 to C5. The number of sympathetic neurons innervating the trachea increased from the moment of birth, reaching a maximum by 10-20 days and then decreasing to age two months. The number of parasympathetic neurons gradually decreased during ontogenesis.     

Effect of 5-hydroxydopamine on the large dense-cored vesicles in the axon terminals of the myenteric ganglia of the guinea-pig stomach

Quantitative ultrastructural analysis revealed that the large dense-cored vesicles in the axon terminals in the myenteric ganglia of the guinea-pig stomach tend to be concentrated towards the ends of the terminals. In guinea-pigs treated with 50 mg/kg 5-hydroxydopamine, diameters of the vesicles were increased and their distribution in the terminals was altered. Treatment with reserpine prior to 5-hydroxydopamine increased the proportion of large dense-cored vesicles and decreased the overall number of vesicles in the terminals. The diameter of the vesicles was increased both in the terminal profiles and in the non-terminal segments of the axons. These observations are consistent with the view that uptake of 5-hydroxydopamine into small vesicles is followed by their transformation into large dense-cored vesicles.     

The innervation of the muscle spindle: a personal history

I present a brief review of current understanding of the innervation of the mammalian muscle spindle, from a personal historical perspective. The review begins with comparative studies on the numbers of spindle afferents and considers how their relative abundance may best be assessed. This is followed by an examination of the distribution and some functional properties of the motor innervation. The primary ending is the subject of the final section, in particular, I look at what can be learned from serial sectioning and volumetric reconstruction, and present new results on a model and simulations concerning sensory terminal deformation during stretch.     

Transmission from intramural excitatory nerves to the smooth muscle cells of the guinea-pig taenia coli

1. A study has been made of transmission from intramural excitatory nerves to the smooth muscle cells of the guinea-pig taenia coli.2. Only ten cells out of eighty gave depolarizing (i.e. excitatory junction potentials, E.J.P.S) on stimulating the intramural nerves, the remaining cells gave hyperpolarizing responses (i.e. inhibitory junction potentials, I.J.P.S). E.J.P.S were recorded in cells which were less than 1 mm away from cells which gave I.J.P.S.3. In some cells stimulation of the intramural nerves with single pulses of maximal strength gave E.J.P.S of about 20 mV amplitude after a latency of 100-200 msec. In quiescent cells these E.J.P.S gave rise to action potentials. Repetitive stimulation above 1 c/s depolarized the membrane for less than about 1 sec, and during the remainder of the stimulation no action potentials fired, even in spontaneous cells.4. In some cells stimulation of the intramural nerves gave an I.J.P. The largest sized I.J.P.S were generally only about half the size of the I.J.P.S recorded in atropinized preparations. The decreased amplitude of the I.J.P.S enabled rebound action potentials to be fired by successive I.J.P.S when the intramural nerves were stimulated at about 1 c/s. At higher frequencies all spontaneous activity was suppressed.5. The effect of neostigmine (10(-9)-10(-7) g/ml.) on the transmission was studied. There was no detectable increase in the number of cells giving E.J.P. responses in the presence of neostigmine.6. The electrophysiological characteristics of intramural excitatory and inhibitory nerve transmission are discussed.     

Effects of hydrogen peroxide on the guinea-pig tracheobronchial mucosa in vivo

Lumenal entry of plasma (mucosal exudation) is a key feature of airway inflammation. In airways challenged with histamine-type mediators and allergen the mucosal exudation response occurs without causing epithelial derangement and without increased airway absorption. In contrast, reactive oxygen metabolites may cause mucosal damage. In this study, involving guinea-pig airways, we have examined effects of H₂O₂ on airway exudation and absorption in vivo. Vehicle or H₂O₂ (0.1 and 0.5 M ) was superfused onto the tracheobronchial mucosal surface through an oro-tracheal catheter. ¹²⁵I-albumin, given intravenously, was determined in tracheobronchial tissue and in lavage fluids 10 min after challenge as an index of mucosal exudation of plasma. The tracheobronchial mucosa was also examined by scanning electron microscopy. In separate animals, ^99mTc-DTPA was superfused 20 min after vehicle or H₂O₂ (0.1 and 0.5 M ) had been given. A gamma camera determined the disappearance rate of ^99mTc-DTPA from the airways as an index of airway absorption. The high dose of H₂O₂ (0.5 M ) produced epithelial damage, increased the absorption of ^99mTc-DTPA (P < 0.001), and increased the exudation of plasma (P < 0.001). Notably, it appeared that all extravasated plasma had entered the airway lumen within 10 min. These data demonstrate that H₂O₂ differs from exudative autacoids such as histamine by causing both epithelial damage and plasma exudation responses. These data also agree with the view that the epithelial lining determines the rate of absorption and is responsible for the valve-like function that allows lumenal entry of extravasated bulk plasma without any increased inward perviousness.     

Innervation of tracheal epithelium and smooth muscle by neurons in airway ganglia

The neurochemical profiles of neurons in ferret tracheal ganglia has been characterized, but their projections to smooth muscle and epithelium in ferret trachea has not been examined. The purpose of this study is to determine the location of cell bodies that project VIP‐, SP‐, and NPY‐containing fibers to the ferret tracheal smooth muscle and epithelium. Segments of ferret trachea were cultured for 0, 1, 3, or 7 days, some in the presence of 3 μm capsaicin. VIP, SP, or NPY nerve fiber density was measured using morphometric procedures. A retrograde tracer, rhodamine‐labeled microspheres, identified neurons projecting to the epithelium. The density of SP fibers in the epithelium was reduced after culture, but VIP innervation was not different. In tracheal smooth muscle, the density of VIP‐ and SP‐IR fibers was not different during the culture period, but NPY fiber density was reduced at all culture times. Capsaicin treatment did not affect nerve fiber density in the tracheal smooth muscle but produced a significant reduction in the density of epithelial VIP‐ and SP‐IR nerve fibers after 1 day. Rhodamine‐labeled microspheres were identified in VIP‐containing nerve cell bodies of the ferret tracheal plexus. VIP innervation to the airway epithelium in ferret originates both from cell bodies in airway ganglia and cell bodies in sensory ganglia. The pathway from airway ganglia suggest the existence of a local reflex mechanisms initiated by epithelial irritation. Anat Rec 254:166–172, 1999. © 1999 Wiley‐Liss, Inc.     

Effects of topical platelet activating factor on the guinea-pig tracheobronchial mucosa in vivo

Platelet activating factor (PAF) has been reported to produce a variety of airway effects including epithelial damage and increased airway-lung absorption of hydrophilic tracers. The present study examines effects of PAF on the guinea-pig tracheobronchial mucosa in vivo. Vehicle with and without PAF (4.0 and 8.0 nmol) was superfused onto the tracheobronchial mucosa. The levels of ¹²⁵I-albumin, previously given intravenously, were determined in tracheobronchial lavage fluids as an index of mucosal exudation of plasma. The mucosa was also examined by scanning electron microscopy. In separate animals, ^99mTc-DTPA (a low molecular weight, 492 Da, hydrophilic tracer) was superfused onto the mucosal surface through an oro-tracheal catheter, together with vehicle or PAF (8.0 nmol). A gamma camera determined the disappearance rate of ^99mTc-DTPA from the airways as an index of mucosal absorption. PAF produced dose-dependent mucosal exudation of plasma up to 20-fold greater than control (P < 0.001). However, PAF did not damage the epithelium and the absorption ability of the airway mucosa was unaffected. The results, in contrast to previous reports, suggest that PAF may not readily damage the airway mucosa even at large exudative doses of the agent. The present finding support the view that the plasticity of the epithelial junctions allows the creation of valve-like paracellular pathways for unidirectional clearance of extravasated plasma into the airway lumen. We suggest that endogenous PAF may participate in first line respiratory defence reactions by causing lumenal entry of bulk plasma without harming the epithelium.     

Nonselective motor innervation of intrafusal fibers in muscle spindles of the rat

Summary Distributions of motor axons to different types of intrafusal fiber were reconstructed from serial 1-m thick transverse sections of six poles of muscle spindle in the rat soleus. Motor axons innervated (dynamic) bag₁ fibers, or (static) bag₂ fibers in conjunction with chain fibers. However, approximately forty percent of axons that supplied the spindles synapsed on both bag₁ and bag₂, or bag₁ and chain fibers. The significance of this co-innervation of dynamic and static intrafusal fibers is discussed relative to the general organization and function of mammalian spindles.     

The modulatory effects of prostaglandins on both excitatory and inhibitory non-adrenergic non-choIinergic neurotransrnission in guinea-pig airways

Johansson -Rydberg , I. G. M., Andersson , R. G. G. & Grundström , N. 1 992 , The modulatory effects of prostaglandins on both excitatory and inhibitory non-adrenergic non-cholinergic neurotransmission in guinea-pig airways. Acta Physiol Scand 144 , 439444. Received 28 August 1 991 , accepted 20 November 1991. ISSN 0001–6772. Department of Pharmacology, University Hospital of Linkoping, Sweden. Guinea-pig trachea and bronchi were used to investigate the effects of indomethacin and prostaglandin E₂ (PGE₂) on non-adrenergic non-cholinergic excitatory (e-NANC) and inhibitory (i-NANC) neurotransmission evoked by electrical field stimulation. Indomethacin potentiated e-NANC responses in bronchi with intact epithelium but had no effect on epithelium-denuded preparations. Inhibitory NANC responses were increased by indomethacin independent of the epithelium. Both i-NANC and e-NANC neurotransmission were suppressed by PGE₂ in a dose-dependent manner. These results indicate that endogenous prostaglandins (e.g. PGE₂) generated from the epithelium have an inhibitory effect on i-NANC and e-NANC nerve responses in airways. The epithelium is presumably not the only source for generation of prostaglandins that are involved in i-NANC neurotransmission.     

First dorsal interosseous muscle of the foot and its innervation

During dissection of the foot region, it is frequently found that some nerve branches run close to the tibial surface of the second metatarsal bone. To investigate the nerve branches, detailed dissection of the first dorsal interosseous muscle was performed in 10 Japanese adult feet with special reference to its innervation. In all specimens the muscle was clearly separated into lateral and medial parts. The branches ran between these parts and innervated the parts. The small dorsal region of the medial part of the muscle was also innervated by a branch of the deep peroneal nerve. Based on its innervation, the muscle appears to be composed of two elements from the flexores breves profundi and an element from the dorsal primordium. A possible schematic model of the origins of this muscle is proposed. Clin. Anat. 12:12–15, 1999. © 1999 Wiley‐Liss, Inc.     

Ontogeny of airway smooth muscle: structure, innervation, myogenesis and function in the fetal lung

Airway smooth muscle (ASM) is an integral component of the primordial lung. It differentiates from the mesenchyme as a ring of cells around the base of the epithelial bud that express smooth muscle-specific proteins. These rapidly form into interlocking bundles that progressively become wider and more compact along the bronchial tree to the trachea. Their orientation is perpendicular to the long axis of the airway. The ASM exhibits rhythmic contractility (i.e. it is a phasic-type smooth muscle) soon after formation, and the spontaneous airway narrowing shifts the lung liquid distally causing expansion of the tubule walls. This stretching is the mechanical stimulus to smooth muscle (SM) myogenesis and lung growth. Neural tissue, i.e. precursor ganglia interconnected by nerve trunks and smaller bundles, forms a sheath over the ASM layer with varicose fibres descending to the muscle. These are guided by glial-derived neurotrophic factor (GDNF) that appears to be produced by ASM. Maturation of neural tissue is slower than the ASM; functional cholinergic innervation is manifest by the early canalicular stage when most neurotransmitters appear.     

Double innervation of the anterior belly of the digastric muscle

We came across a very rare case in which the anterior belly of the digastric muscle was innervated by the twigs of the facial nerve in addition to those of the mylohyoid nerve. The anomaly was discovered in the cadaver of an 84-year-old Japanese male bequeathed for a training seminar in gross anatomy at Kumamoto University in 2003. One twig issued from the marginal mandibular branch of the facial nerve and entered the central region of the anterior belly of the digastric muscle on the lower surface. The other twig issued from the stylohyoid branch of the facial nerve, descended along the lateral margin of the stylohyoid muscle and entered the anterior belly of the digastric muscle on the lower surface near the intermediate tendon. The twig from the marginal mandibular branch was distributed to the shallow (lower) and central region near the medial margin of the anterior belly. The twig from the stylohyoid branch was distributed to the shallow and lateral region of the anterior belly. These two twigs communicated with the mylohyoid nerve at several peripheral parts. Textbooks on general anatomy make mention of only one nerve, the mylohyoid, supplying the anterior belly of the digastric muscle. However, the present case manifests that the anterior belly receiving twigs from the mylohyoid and facial nerves is formed with the second brachial component as well as the first.     

Antagonism of non-cholinergic excitatory junction potentials in the guinea-pig ileum by a substance P analogue antagonist

In the presence of atropine electrical transmural stimulation (using repetitive volleys, e.g. 3 pulses at 50 Hz applied every 4 s) of full thickness longitudinal strips of guinea-pig ileum produced non-cholinergic excitatory junction potentials (EJPs) and inhibitory junction potentials (IJPs) in the circular muscle layer. After abolition of the IJPs with apamin, the non-cholinergic EJPs clearly showed facilitation. In the presence of apamin and the substance P analogue antagonist, [D-Arg1,D-Pro2,D-Trp7-9,Leu11]-substance P (SPA), the non-cholinergic EJPs were reduced by 60-90%; transmural stimulation now revealed an apamin-resistant IJP followed by a slow depolarization. The atropine-resistant EJPs are probably caused by the release of substance P (or a similar compound) and are likely to underlie the non-cholinergic contractions reported to occur in this tissue.     

Attenuating effect of H+K+ATPase inhibitors on airway cough hypersensitivity induced by allergic airway inflammation in guinea-pigs

BACKGROUND: Gastrooesophageal reflux (GER) is a frequent cause of chronic cough. Several investigators have indicated that inhibitors of H(+)K(+)ATPase (proton pump inhibitors; PPIs) could relieve coughing via inhibition of acid reflux. However, we considered that PPIs might directly inhibit increased cough reflex sensitivity. OBJECTIVE: The present study was designed to examine whether PPIs directly inhibit antigen-induced increase in cough reflex sensitivity and to elucidate the mechanism. METHODS: Actively sensitized guinea-pigs were challenged with aerosol antigen (ovalbumin, OVA) and cough reflex sensitivity to inhaled capsaicin was measured 24 h later. The PPIs (omeprazole and rabeprazole) or the histamine H(2) blocker cimetidine were administered intraperitoneally 1 h before OVA challenge and before measuring cough reflex sensitivity, then bronchoalveolar lavage fluid (BALF) was immediately collected. The pH of the fluid obtained by bronchial washing was determined after examining the effect of rabeprazole on the cough response to capsaicin. RESULTS: The number of coughs elicited by capsaicin was significantly increased 24 h after challenge with OVA compared with saline, indicating antigen-induced increase in cough reflex sensitivity. Both PPIs dose dependently and significantly inhibited antigen-induced cough hypersensitivity. Omeprazole did not influence the antigen-induced increase in the total number of cells or ratio (%) of eosinophils in BALF. Cimetidine did not affect the antigen-induced cough hypersensitivity or cellular components of BALF. The pH of the bronchial washing fluid was significantly decreased in antigen-challenged animals. Rabeprazole did not affect the antigen-induced decrease in the pH of bronchial washing fluid. CONCLUSION: These findings show that PPIs, but not histamine H(2) blockers, can directly decrease antigen-induced cough reflex hypersensitivity, while the mechanism remains unclear.     

Shared motor innervation between dynamic and static intrafusal muscle fibers in the monkey

Distributions of 25 motor axons to 60 intrafusal muscle fibers of 10 poles of monkey spindle were reconstructed from serial 1 micron thick transverse sections of lumbrical muscles. About 44% of motor axons co-innervated two or more types of intrafusal fiber. The (dynamic) bag1 fiber shared motor innervation with the (static) bag2 or chain fibers in about 50% of spindle poles. Activation of single intrafusal fibers independent of the other fibers of the same intrafusal bundle occurs to a lesser degree in spindles of monkeys than in spindles of cats. Functional implications of this pattern of motor innervation are discussed.     

Selective inhibition by dactinomycin of NANC sensory bronchoconstriction and [125I] NKA binding due to NK-2 receptor antagonism

Y.-P. Lou, P. Delay -Goyet & J. M. Lundber g. 1991. Selective inhibition by dactinomycin of NANC sensory bronchoconstriction and [¹²⁵I]NKA binding due to NK-2 receptor antagonism. Acta Physiol Scand 144 , 221–231. Received 6 May 1991, accepted 13 September 1991. ISSN 0001–6772. Department of Pharmacology, Karolinska Institutet, Stockholm. In the present study, dactinomycin (m) inhibited the non-adrenergic, non-cholinergic bronchoconstriction upon antidromic vagal nerve stimulation (1 Hz for 1 min) in the isolated perfused guinea-pig lung by 84%. The release of calcitonin gene-related peptide was unchanged, however, suggesting a postjunctional action. Dactinomycin (10^-5, 5 × 10^-5 m) also reduced non-adrenergic non-cholinergic bronchial contractions (maximally by 75%) induced by electrical field stimulation or capsaicin, while the cholinergic component and non-adrenergic non-cholinergic relaxation remained intact. The neurokinin-2 receptor antagonist l-659 877 (10^-6 m) had a similar effect as dactinomycin, inhibiting the non-adrenergic non-cholinergic bronchial contractions by 69%, while the neurokinin-1 receptor antagonist CP-96,345 (10^-6m) had no effect. The bronchoconstriction evoked by neurokinin A, the selective neurokinin-2 receptor agonist Nle¹⁰neurokinin A (4–10) and capsaicin was markedly inhibited by dactinomycin while the contraction induced by substance P (SP), the selective neurokinin-1 receptor agonist Sar⁹Met(0₂)¹¹SP, endothelin-1 and acetyl-choline was not affected. In autoradiographic experiments on guinea-pig lung, [¹²⁵I]neurokinin A-labelled sections showed dense binding in the bronchial smooth muscle layer. Dactinomycin inhibited the specific binding of [²⁵1]neurokinin A in a concentration-dependent manner (IC₅₀= 6.3 × 10^-6 m) and 66% of [¹²⁵I]neurokinin A total binding was inhibited by 10^-4 M dactinomycin. In the rat colon, [¹²⁵I]neurokinin A binding to neurokinin-2 sites on circular smooth muscle was inhibited by dactinomycin with an IC₅₀ value of 7.9 × 10^-6 M. Dactinomycin failed to reduce increased nerve-evoked contractions or those caused by Nle¹⁰neurokinin A (4–10) per se in the rat vas deferens, which are considered to be mediated by neurokinin-2 receptor activation. In the rat portal vein, dactinomycin did not influence the contractions caused by the neurokinin-3 selective agonist Pro⁷neurokinin B. In conclusion, dactinomycin selectively inhibited neurokinin-2 receptor activation in guinea-pig lung and rat colon, but not in rat vas deferens, which may depend on the existence of different neurokinin-2 receptor subtypes. Neurokinin A is most likely the main endogenous excitatory non-adrenergic non-cholinergic transmitter in guinea-pig bronchi.     

Sympathetic innervation of human muscle spindles

The aim of the present study was to investigate the presence of sympathetic innervation in human muscle spindles, using antibodies against neuropeptide Y (NPY), NPY receptors and tyrosine hydroxylase (TH). A total of 232 muscle spindles were immunohistochemically examined. NPY and NPY receptors were found on the intrafusal fibers, on the blood vessels supplying muscle spindles and on free nerve endings in the periaxial space. TH‐immunoreactivity was present mainly in the spindle nerve and vessel. This is, to our knowledge, the first morphological study concerning the sympathetic innervation of the human muscle spindles. The results provide anatomical evidence for direct sympathetic innervation of the intrafusal fibers and show that sympathetic innervation is not restricted to the blood vessels supplying spindles. Knowledge about direct sympathetic innervation of the muscle spindle might expand our understanding of motor and proprioceptive dysfunction under stress conditions, for example, chronic muscle pain syndromes.