Patchouli alcohol improved diarrhea-predominant irritable bowel syndrome
by regulating excitatory neurotransmission in the myenteric plexus of
rats
Abstract
Background and Purpose: Irritable bowel syndrome (IBS) is usually
associated with chronic gastrointestinal disorders. Its most common
subtype is accompanied with diarrhea (IBS-D). The enteric nervous system
(ENS) modulates major gastrointestinal motility and functions whose
aberration may induce IBS-D. The enteric neurons are susceptible to
long-term neurotransmitter level alterations. The patchouli alcohol
(PA), extracted from Pogostemonis Herba, has been reported to regulate
neurotransmitter release in the ENS, while its effectiveness against
IBS-D and the underlying mechanism remain unknown. Experimental
Approach: In this study, we established an IBS-D model in rats through
chronic restraint stress. We administered the rats with 5, 10, and 20
mg/kg of PA for intestinal and visceral examinations. The longitudinal
muscle myenteric plexus (LMMP) neurons were further
immunohistochemically stained for quantitative, morphological, and
neurotransmitters analyses. Key Results: We found that PA decreased
visceral sensitivity, diarrhea symptoms and intestinal transit in the
IBS-D rats. Meanwhile, 10 and 20 mg/kg of PA significantly reduced the
proportion of excitatory LMMP neurons in the distal colon, decreased the
number of acetylcholine (Ach)- and substance P (SP)-positive neurons in
the distal colon and restored the levels of Ach and SP in the IBS-D
rats. Conclusion and Implications: These findings indicated that PA
modulated LMMP excitatory neuron activities, improved intestinal
motility and alleviated IBS-induced diarrheal symptoms, suggesting the
potential therapeutic efficacy of PA against IBS-D.