Modulation of the peristaltic reflex of rat ileum segments by STW 5 (Iberogast®)

Dyspepsia and motility related disorders of the gastrointestinal tract are increasingly treated with herbal drugs. This especially applies to STW 5 (Iberogast®), a fixed combination of standardized plant extracts, for which clinical efficacy has been proven in several modern randomized controlled double blind studies [1, 2]. But there still remain unanswered questions about the possible mechanisms of action by which the plant extracts induce the beneficial effects. Aim of the present study was to investigate whether plant extracts influence the reflex pathways underlying the peristaltic reflex of rat small intestine.

The myenteric pathways of the peristaltic reflex were studied in 10cm ileum segments and peristaltic activity was stimulated by electrical stimulation in the middle of the segments. Ascending and descending reflex responses were recorded by using force transducers. Areas under the contraction curves were evaluated. Drugs were added in a cumulative manner. Concentrations are given as dilution of the standardized fluid plant extract in organ bath medium.

The extracts had individual, reproducible effects on the elicited reflex responses, showing a clear concentration dependency (e.g. peppermint leaf extract on ascending contraction: 1:1000: -10.1±4.0%; 1:500: -8.8±6.6%; 1:250: –17.3±4.7%; 1:167: –39.5±13.5%; 1:83: -55.4±15.5; 1:50: -58.9±15.6). All observed effects were fully reversible after washout and were blocked by tetrodotoxin proving the underlying neuronal mechanisms. Contractile responses were abolished by atropine proving that they are mediated by cholinergic mechanisms.

The observed effects of STW 5 and its components on gastrointestinal motility are a clue for understanding the pharmacological mechanisms underlying the relief in patient symptoms.

References: 1. Holtmann, G. et al. (2004), Wien Med Wochenschr 154:21–22. 2. Madisch, A. et al. (2004), Aliment. Pharmacol. Ther. 19:271–279.