Herbal extracts modulate the amplitude and frequency of slow waves in circular smooth muscle of mouse small intestine

Background: Herbal preparations like STW 5 (Iberogast(R)) are
widely used drugs in the treatment of dyspepsia and
motility-related disorders of the gastrointestinal tract. STW 5 is
a phytotherapeutic agent consisting of a fixed mixture of 9
individual plant extracts. The electrophysiological mechanisms of
action of STW 5 remain obscure. Aim: The aim of the present study
was to investigate whether herbal extracts influence
electrophysiological parameters of the small intestine. For this
purpose, the resting membrane potential (RMP) and the slow wave
rhythmicity of smooth muscle cells of mouse small intestine were
observed. Methods: Intracellular recordings of smooth muscle cells
of the circular muscle layer of mouse small intestine were
performed using standard microelectrode techniques. After
dissection of the mucosa, the small intestine was placed in an
organ bath and a microelectrode was applied on a circular smooth
muscle cell. The RMP and the amplitude of slow waves were measured
in millivolts. Results: The RMP of smooth muscle cells was - 59 +/-
1.3 mV. This RMP was significantly depolarized by STW 5 ( 9.6 +/-
1.6 mV); the depolarizing effects can be mainly attributed to the
constituents of matricariae flos, angelicae radix and chelidonii
herba. The basal frequency of small intestinal slow waves was 39.5
+/- 1.4 min(-1) and the amplitude was 23.1 +/- 0.9 mV. STW 5
significantly reduced the amplitude and frequency of the slow waves
( 11.7 +/- 0.8 mV; 33.5 +/- 3.4 min(-1)). This effect on slow waves
represents the sum of the effects of the 9 phytoextracts. Whereas
angelicae radix and matricariae flos completely blocked slow wave
activity, Iberis amara increased the frequency and amplitude,
chelidonii herba reduced the frequency and amplitude of the slow
waves, mentae piperitae folium reduced the frequency and left
amplitude unchanged and liquiritae radix, carvi fructus and
melissae folium had no effects. Conclusion: Herbal extracts cause
changes in smooth muscle RMP and slow wave rhythmicity, up to
reversible abolition, by blockade of large conductance Ca2+
channels and other not yet identified mechanisms. In herbal
preparations like STW 5 these effects add up to a total effect and
this study indicates that herbal preparations which are widely used
in dyspepsia and motility-related disorders have characteristic,
reproducible, reversible effects on small intestinal
electrophysiology. Copyright (C) 2005 S. Karger AG, Basel.