An excessive, irritable, productive or non-productive coughing associated with airway inflammation belongs to pathological cough. Increased activation of airway vagal nociceptors in pathological conditions results from dysregulation of the neural pathway that controls cough. A variety of mediators associated with airway inflammation overstimulate these vagal airway fibers including C-fibers leading to hypersensitivity and hyperreactivity. Because current antitussives have limited efficacy and unwanted side effects there is a continual demand for the development of a novel more effective antitussives for a new efficacious and safe cough treatment. Therefore, inhibiting the activity of these vagal C-fibers represents a rational approach to the development of effective antitussive drugs. This may be achieved by blocking inflammatory mediator receptors or by blocking the generator potential associated with the specific ion channels. Because voltage-gated sodium channels (NaVs) are absolutely required for action potentials initiation and conduction irrespective of the stimulus, NaVs become a promising neural target. There is evidence that NaV1.7, 1.8 and 1.9 subtypes are predominantly expressed in airway cough-triggering nerves. The advantage of blocking these NaVs is suppressing C-fiber irrespective to stimuli, but the disadvantage is that by suppressing the nerves is may also block beneficial sensations and neuronal reflex behavior. The concept is that new antitussive drugs would have the benefit of targeting peripheral airway nociceptors without inhibiting the protective cough reflex.
- MeSH
- akční potenciály účinky léků fyziologie MeSH
- antitusika farmakologie terapeutické užití MeSH
- blokátory sodíkových kanálů řízených napětím farmakologie terapeutické užití MeSH
- kašel farmakoterapie patofyziologie MeSH
- lidé MeSH
- nociceptory účinky léků metabolismus MeSH
- sodíkové kanálky řízené napětím fyziologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Clinical studies showed that GABA(B) receptor agonists improve symptoms in patients with gastroesophageal reflux disease. One proposed mechanism of this effect is direct inhibition of the gastroesophageal vagal tension mechanosensors by GABA(B) agonists leading to reduction of reflux. In addition to tension mechanosensors, the vagal nodose ganglion supplies the esophagus with nociceptive C-fibers that likely contribute to impairment of esophageal reflex regulation in diseases. We hypothesized that GABA(B) agonists inhibit mechanically-induced activation of vagal esophageal nodose C-fibers in baseline and/or in sensitized state induced by inflammatory mediators. Ex vivo extracellular recordings were made from the esophageal nodose C-fibers in the isolated vagally-innervated guinea pig esophagus. We found that the selective GABA(B) agonist baclofen (100-300 microM) did not inhibit activation of esophageal nodose C-fibers evoked by esophageal distention (10-60 mmHg). The mechanical response of esophageal nodose C-fibers can be sensitized by different pathways including the stimulation of the histamine H(1) receptor and the stimulation the adenosine A(2A) receptor. Baclofen failed to inhibit mechanical sensitization of esophageal nodose C-fibers induced by histamine (100 microM) or the selective adenosine A(2A) receptor agonist CGS21680 (3 nM). Our data suggest that the direct mechanical inhibition of nodose C-fibers in the esophagus is unlikely to contribute to beneficial effects of GABA(B) agonists in patients with esophageal diseases.
- MeSH
- aferentní nervové dráhy účinky léků fyziologie MeSH
- agonisté receptorů GABA-A aplikace a dávkování MeSH
- baklofen aplikace a dávkování MeSH
- ezofágus účinky léků inervace fyziologie MeSH
- ganglion inferius účinky léků fyziologie MeSH
- morčata MeSH
- nervový útlum účinky léků fyziologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- zvířata MeSH
- Check Tag
- morčata MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Cough is a common and important symptom of asthma and allergic rhinitis. Previous experimental evidence has shown enhanced cough sensitivity during early phase of experimental allergic rhinitis in guinea pigs. We hypothesized that airway inflammation during the late phase response after repeated nasal antigen challenge may affect the afferent sensory nerve endings in the larynx and tracheobronchial tree and may also modulate cough response. In the present study we evaluated the cough sensitivity during a period of early and late allergic response in sensitized guinea pigs after repeated nasal antigen challenges. Forty-five guinea pigs were sensitized with ovalbumin (OVA). Four weeks later 0.015 ml of 0.5 % OVA was intranasally instilled to develop a model of allergic rhinitis that was evaluated from the occurrence of typical clinical symptoms. Animals were repeatedly intranasally challenged either by OVA (experimental group) or by saline (controls) in 7-day intervals for nine weeks. Cough was elicited by inhalation of citric acid aerosols. Cough was evaluated at 1 or 3 h after the 6th nasal challenge and 17 or 24 h after the 9th nasal challenge. The cough reflex was significantly increased at 1 and 3 h after repeated nasal challenge in contrast to cough responses evoked at 17 and 24 h after repeated nasal challenge. In conclusion, enhanced cough sensitivity only corresponds to an early allergic response after repeated nasal challenges.
- MeSH
- alergie imunologie komplikace MeSH
- financování vládou MeSH
- interpretace statistických dat MeSH
- kašel chemicky indukované MeSH
- kyselina citronová imunologie škodlivé účinky MeSH
- modely u zvířat MeSH
- morčata imunologie MeSH
- ovalbumin aplikace a dávkování imunologie MeSH
- rýma etiologie imunologie MeSH
- zánět imunologie komplikace mikrobiologie MeSH
- zvířata MeSH
- Check Tag
- morčata imunologie MeSH
- zvířata MeSH
- Publikační typ
- srovnávací studie MeSH
