The methanol extract of the leaves of P. incarnata was evaluated for its antiasthmatic effects against acetylcholine chloride (Ach)-induced-bronchospasm in guinea-pigs at doses of 50, 100 and 200 mg/kg. Using a 7-day treatment regimen, significant prevention of dyspnoea-related-convulsions was noted in the animals treated with a 100 mg/kg dose of this extract. No preventive effect was exhibited by the 50 mg/kg dose and at a higher dose, i.e. 200 mg/kg, the preventive effects against Ach-chloride-induced-dyspnoea were also reduced. This may be due to defective alpha-adrenoceptor function reported after excessive or continuous administration of an alpha-receptor agonist.
Copyright 2003 John Wiley & Sons, Ltd.