Antitussive effects of the peripherally restricted GABA(B) receptor agonist lesogaberan in guinea pigs: comparison to baclofen and other GABA(B) receptor-selective agonists

BACKGROUND: Gastroesophageal reflux disease (GERD) is a common cause of chronic cough. Both acid and nonacid reflux is thought to play a role in the initiation of coughing and cough hypersensitivity. The GABA(B) receptor agonist lesogaberan was developed as a peripherally restricted anti-reflux therapy that reduces the frequency of transient lower esophageal sphincter relaxations (TLESR; the major cause of reflux) in animals and in patients with GERD. GABA(B) receptor agonists have also been shown to possess antitussive effects in patients and in animals independent of their effects on TLESR, suggesting that lesogaberan may be a promising treatment for chronic cough. METHODS: We have assessed the direct antitussive effects of lesogaberan (AZD3355). The effects of other GABA(B) receptor agonists were also determined. Coughing was evoked in awake guinea pigs using aerosol challenges with citric acid. RESULTS: Lesogaberan dose-dependently inhibited citric acid evoked coughing in guinea pigs. Comparable effects of the GABA(B) receptor agonists baclofen and 3-aminopropylphosphinic acid (3-APPiA) on cough were also observed. Baclofen produced obvious signs of sedation and respiratory depression. By contrast, both lesogaberan and 3-APPiA (both inactivated centrally by GABA transporters) were devoid of sedative effects and did not alter respiratory rate. CONCLUSIONS: Together, the data suggest that lesogaberan and related GABA(B) receptor agonists may hold promise as safe and effective antitussive agents largely devoid of CNS side effects.