Spasmogenic Activity of the Aqueous Methanolic Extract of Unripe Carica papaya Fruit in Isolated Uterine Muscle of the Rat

Aims: This study investigated the effect of the aqueous methanolic extract of unripe Carica papaya (AMEUCP) on uterine contractility and its possible mechanism(s) of action.

Place and Duration of the Study: The study was carried out in the Department of Veterinary Surgery and Theriogenology, Michael Okpara University of Agriculture, Umudike, Nigeria and the Department of Veterinary Physiology and Pharmacology, University of Nigeria, Nsukka, Nigeria between February and June 2013.

Methods: Fresh mature unripe pawpaw fruits were obtained from Nsukka and extracted by cold maceration with 80% methanol for 48 hours and then concentrated to dryness. Estrogenised uterine muscle strips were harvested from sexually mature non-gravid female rats (200-250 g). In each experiment, a strip of about 1cm was mounted in a 50ml organ bath containing Krebs’ physiological salt solution, connected to an isometric electronic force displacement transducer and an oscillograph. The following drugs were used as receptor agonists or antagonist: Salbutamol (0.2 µM), Isoprenaline (0.1 µM), Prazosin (10 nM), Propranolol (0.2 µM), cholinergic receptor antagonist; Atropine (240 nM). The extract and the standard drugs were applied at concentrations corresponding to the final bath concentration.

Results: The extract elicited forceful contraction of the uterus in a dose dependent manner and the mechanism of this contraction has been shown to involve the stimulation of myometrial cholinergic and alpha adrenoceptors, mobilization of calcium ion from the extracellular fluid and partly by release of calcium ions from the sarcoplasm.

Conclusion: These findings justify the traditional use of the plant for its uterotonic properties while deciphering its possible mechanisms of action may serve as a focal point for development of new uterotonics or oxytocics.