Antitussive Effect of Naringin on Experimentally Induced Cough in Guinea Pigs

The mechanism of action of naringin has been investigated in different models of experimentally induced cough in guinea pigs. In contrast to codeine phosphate (6 mg/kg, intravenous administration [i.v.]), naringin (15, 30, and 60 mg/kg, i.v.) had no central antitussive effect on cough elicited by electrical stimulation of the superior laryngeal nerve. Naringin (0.5, 1.0, and 2.0 mu mol) could not prevent the cough reflex induced by stimulation of the trachea after intracerebroventricular injection (i.c.v.), while codeine phosphate (0.5 mu mol) was highly effective. Further characterizing the peripheral mechanism of naringin, we found that its effect (50 mg/kg, i.v.) was not affected by the depletion of sensory neuropeptides, whereas levodropropizine (10 mg/kg, i.v.) lost its capacity to prevent cough in the capsaicin-desensitized guinea pig. Furthermore, pretreatment with glibenclamide (10 mg/kg, intraperitoneal [i.p.]) significantly reduced the antitussive effect of pinacidil (5 mg/kg, subcutaneous [s.c.]), but could not antagonize the antitussive effect of naringin (30 mg/kg, s.c.). Our present results suggest that naringin is not a central antitussive drug. And naringin does not exert its peripheral antitussive effect through either the sensory neuropeptides system or the modulation of ATP-sensitive K+ channels.