Possible role of serotonin in the gastrokinetic activity of Amorphophallus paeoniifolius tuber

Abstract

Background: Amorphophallus paeoniifolius (Dennst.) Nicolson (Araceae) tuber is consumed by various tribes for the treatment of constipation, hemorrhoids, functional dyspepsia and abdominal pain as ethnomedicinal practices. In our previous study, the tuber extract showed alteration of gastric emptying in healthy rats and ameliorated the gastrointestinal motor disorders, constipation and piles. Aim of the study: Hence, the present study evaluated the effect of Amorphophallus paeoniifolius tuber on experimentally-induced delayed gastric emptying in rats as well as investigated the plausible mechanism involved therein. Methods: Methanolic extract of Amorphophallus paeoniifolius (APME) was orally administered at the doses of 125, 250 and 500 mg/kg for 7 days. Delayed gastric emptying was induced in rats by cisplatin (10 mg/kg, i.p.) on the last day of extract treatment and gastric emptying was studied. To study the involvement of serotonergic system, the effect of APME (500 mg/kg) was investigated on gastric emptying in p-chlorophenylalanine (PCPA, a serotonergic neurotoxin) treated rats. Ex-vivo studies in isolated tissue preparation were also conducted to test the effect of APME on fundus contractility. Results: APME significantly reversed the delayed gastric emptying caused by cisplatin comparable to standard prokinetic drug, metoclopramide. Interestingly, the co-administration of sub-maximal doses of APME and metoclopramide showed synergistic effect on delayed gastric emptying. Further, in PCPA treated rats, APME (500 mg/kg) did not show any significant influence on delayed gastric emptying similar to metoclopramide. In Ex-vivo studies, the contractile response of APME remained unaltered in presence of atropine while it was potentiated significantly (P < 0.001) in presence of 5-HT as compared to the individual responses of 5-HT or APME. Phytochemical studies revealed the presence of betulinic acid in APME which is partial serotonergic agonist. Conclusion: The tuber of Amorphophallus paeoniifolius exhibited gastrokinetic activity and may be beneficial on functional dyspepsia. The effect may be ascribed to modulation of serotonergic neurotransmission in GIT.