STW 5 (Iberogast) reduces afferent sensitivity in the rat small intestine.
BACKGROUND
A limited number of drugs are available for the treatment of functional dyspepsia and irritable bowel syndrome. The efficacy of STW 5 (Iberogast) was previously shown in clinical trials. Since visceral hypersensitivity seems to be the prime pathomechanism of functional gastro-intestinal disorders, the aim of this study was to explore whether STW 5 reduces intestinal afferent sensitivity in the upper gastrointestinal tract.


METHODS
Two groups of male Wistar rats were pretreated with either the herbal preparation STW 5 or its vehicle (30.8% ethanol). Then, after 2h, general anesthesia was induced by pentobarbitone (60 mg kg(-1)i.p.) and extracellular multi-unit afferent recordings were obtained from mesenteric afferents innervating the proximal jejunum. The intestinal afferent nerve response to increasing doses of 5-HT and bradykinin were quantified as well as afferent discharge following a ramp distension of the adjacent intestinal loop from 0 to 60 cm H(2)O.


RESULTS
Afferent discharge to 5-HT and bradykinin increased dose-dependently. Following the different doses of 5-HT, the peak in afferent nerve discharge was always reduced after pretreatment with STW 5 compared to controls with a response of 110+/-5 imp s(-1) after STW 5 and 128+/-3 in vehicle controls at the maximum dose (40 microg kg(-1); p<0.05; mean+/-SEM). For bradykinin, afferent responses were reduced following STW 5 at the 20 and 40 microg kg(-1) dose but not at 10 microg kg(-1) (40 microg kg(-1)176+/-7 imp s(-1) following STW 5 versus 200+/-6 imp s(-1) in controls; p<0.05). The ramp distension of the intestinal loop stimulated a rise in intestinal afferent nerve discharge that was always lower in the STW 5 pretreated group compared to vehicle controls with the exception of the discharge rate at the pressure level of 0 and 20 cm H(2)O (all other pressures up to 60 cm H(2)O p<0.05).


CONCLUSIONS
Sensitivity of intestinal afferents to mechanical and chemical stimuli is reduced following treatment with the herbal preparation STW 5. This mechanism may help to explain why STW 5 relieves dyspeptic and bowel symptoms in patients.
Müller
M H
MH
Ludwig-Maximilians University, Department of Surgery, Munich, Germany.
Liu
C-Y
CY
Glatzle
J
J
Weiser
D
D
Kelber
O
O
Enck
P
P
Grundy
D
D
Kreis
M E
ME
D000344:Afferent Pathways / Q000187:drug effects; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D005765:Gastrointestinal Agents / Q000494:pharmacology*; D007421:Intestine, Small / Q000187:drug effects* / Q000294:innervation*; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects*; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology; D013314:Stress, Mechanical
D005765:Gastrointestinal Agents; D010936:Plant Extracts; C039964:iberogast; D012701:Serotonin; D001920:Bradykinin