The role of nitric oxide and opioid receptors in antispasmodic activity of Petroselinum crispum (parsley) seed extract on rat ileum

Parsley seed inhibits rat ileum contraction. In the rat intestine, Nitric oxide (NO) has been suggested to participate in nonadrenergic noncholinergic (NANC) relaxation of longitudinal smooth muscle. In addition, endogenous opioid peptides and opiate drugs affect a variety of gastrointestinal (GI) functions, including motility. Studies have shown that opioids inhibit electrically induced smooth muscle contractions. The aim of present study was to investigate the involvement of opioid receptors and NO in antispasmodic activity of parsley seed hydroalcoholic extract. In this study, 28 rats were randomly divided into 4 equal groups: 1) the effect of different concentrations of extract on KCl-induced contraction, 2) the effect of L-NAME on extract function, 3) the effect of naloxone on extract function, 4) the long-term effect of KCl. A piece of terminal portion of male rat ileum (2 cm) was dissected out and mounted in an organ bath containing air bubbled Tyrode solution (37 οC, pH=7.4) with 1 g initial tension and ileal contractions induced by KCl was recorded by an isotonic transducer. Antispasmodic activity of extract after tissue incubation was evaluated using Nω-nitro-L-arginine methyl ester (L-NAME) and naloxone. The spasmolytic effect of the cumulative concentrations of the extract (0.1-0.8 mg/ml) was not reduced sensibly after tissue incubation with L-NAME (100 μM, 30 min) as a nitric oxide synthase inhibitor and naloxone (1µM, 30 min) as a non-selective opioid receptor antagonist. Although Parsley seed extract inhibit rat ileum contraction, it seems that NO and opioid receptors are not involved in this activity.