The herbal preparation STW 5 (Iberogast) desensitizes intestinal afferents in the rat small intestine.
BACKGROUND
Visceral hypersensitivity in the upper gastrointestinal tract is a potential pathomechanism of functional dyspepsia. The herbal preparation STW 5 (Iberogast) provides symptomatic relief for this condition. We aimed to investigate whether STW 5 modulates intestinal afferent sensitivity.


METHODS
The herbal preparation STW 5 or vehicle (30.8% ethanol) were administered orally in male Wister rats. After 2 h animals were anaesthetized and extracellular multi-unit intestinal afferent nerve recordings were secured from the neurovascular bundle of the mesentery in the proximal jejunum. Afferent discharge to ramp distension of the intestinal loop (0-60 cm H2O) and dose-response curves for i.v. bradykinin (10, 20 and 40 microg kg(-1)) and 5-HT (5, 10, 20 and 40 microg kg(-1)) were recorded.


RESULTS
Baseline discharge was not different between the vehicle and treatment group. Ramp distension was followed by a pressure dependent increase in afferent nerve discharge that was decreased following STW 5 pretreatment for all distending pressures reaching 147 +/- 8 impulses s(-1) (imp s(-1)) following STW 5 vs 171 +/- 5 imp s(-1) following vehicle at 60 cm H2O (mean +/- SEM; P < 0.05). A dose-dependent increase in afferent discharge was observed for 5-HT and bradykinin. Following STW 5 pretreatment, afferent discharge was reduced at all doses of 5-HT to 110 +/- 5 at the maximum dose after STW 5 and 128 +/- 3 imp s(-1) in controls (all P < 0.05). Afferent discharge to bradykinin was similarly reduced at 20 and 40 microg kg(-1) but not at 10 microg kg(-1) of bradykinin with a discharge rate of 176 +/- 7 imp s(-1) following STW 5 and 200 +/- 6 imp s(-1) in controls at 40 microg kg(-1) (P < 0.05).


CONCLUSIONS
The preparation STW 5 reduces intestinal afferent nerve discharge following chemical and mechanical stimuli, while baseline discharge is not affected. This effect of STW 5 on afferent sensitivity may contribute to its therapeutic relief of dyspeptic symptoms.
Liu
C-Y
CY
Department of Surgery, Ludwig-Maximilians University, Hospital Grossharden, Munich, Germany.
Müller
M H
MH
Glatzle
J
J
Weiser
D
D
Kelber
O
O
Enck
P
P
Grundy
D
D
Kreis
M E
ME
D000818:Animals; D007421:Intestine, Small / Q000187:drug effects* / Q000294:innervation*; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology*; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D010936:Plant Extracts; C039964:iberogast