Abstract
Chronic cough is a troublesome problem and it is frequently associated with diseases such as gastroesophageal reflux, asthma and upper airway diseases—so called diagnostic triade. The magnitude and severity of cough is strongly associated with the ongoing nasal inflammation in subjects with rhinosinusitis and treatment of nasal inflammation leads to the down regulation of pathologically up-regulated cough. Histamine plays a key role in the inflammation of the upper airways of different aetiologies; therefore histamine receptors seem to be promising targets. The aim of our study was to ascertain the effect of H3R agonist imetit and H3R antagonist thioperamide on cough and symptoms of allergic rhinitis (AR) in an animal model of upper airway cough syndrome in ovalbumin sensitized guinea pigs. OVA sensitized guinea pigs (n = 10) were repeatedly challenged with i.n. allergen-OVA to induce allergic rhinitis and to enhance cough reflex according to the validated model of experimental allergic rhinitis. Animals were pre-treated by i.p. administration of imetit (1 mg/kg and 2 mg/kg of body weight) and thioperamide 30 min. prior i.n. OVA administration. Rhinitis evaluation was based on the occurrence of typical symptoms. The effect on cough was assessed from the response to inhalation of citric acid (0.4 M, 10 min), final cough count and cough latency were analysed from the airflow traces, cough motor pattern and the cough sound. AR up-regulated the cough response from 9 ± 2 to 16 ± 1 cough per provocation, med ± IQR, p < 0.05 and shortened cough latency. Imetit (1 mg/kg) suppressed nasal symptoms and decreased number of cough from 16 ± 1 to 12 ± 1; however the data did not reach significance. Imetit (2 mg/kg) significantly suppressed the nasal symptoms, and number of coughs from 16 ± 1 to 6 ± 2, med ± IQR, p < 0.05. Thioperamide (5 mg/kg of body weight) did not have expected effects on tested parameters. H3R agonist imetit, unlike H3R antagonist thioperamide has antitussive potential and ability to suppress nasal symptoms in animal model of allergic rhinitis.
Highlights
Chronic cough is a quite common presentation to both primary and secondary care, with prevalence in the community in a range of 9% - 33% [1]
We focused on histamine H3 receptor (H3R)
Presence of early phase of allergic rhinitis led to significant increase of cough per provocation (Figure 1) from 9 ± 2 to 16 ± 1, med ± IQR, p < 0.05 and significantly shortened cough latency from 189 ± 20 s to 66 ± 18 s (Figure 2)
Summary
Chronic cough (cough of more than 8 weeks duration) is a quite common presentation to both primary and secondary care, with prevalence in the community in a range of 9% - 33% [1]. The management of patients with chronic cough is often problematic, with relatively few therapeutic options. Chronic cough has been associated with complex aetiology, but it is considered to be rather “one syndrome” mainly mediated by hypersensitivity of cough-related airway afferents [3]. Upper airway disease (rhinosinusitis) is one of the most commonly identified causes of chronic cough. Animal models and studies in subjects with upper airway diseases showed that cough sensitivity correlates with the presence of nasal inflammation and magnitude of nasal symptoms. Effective treatments of local inflammation reduced significantly the magnitude of nasal symptoms and reduced coughing and cough hypersensitivity [2] [4]
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