Abstract
Irritable bowel syndrome (IBS) is characterized by chronic visceral hypersensitivity that companied by altered bowel movement. However, the treatment options are very limited. The aim of this study was to investigate effects of electroacupuncture (EA) on visceral hypersensitivity in a rat model of IBS and to explore the underlying mechanisms of EA effects. Visceral hypersensitivity was established by neonatal maternal deprivation (NMD) in male rats on postnatal days 2 - 15. Behavioral experiments were conducted at the age of 7 weeks. Treatment with EA at Zusanli (stomach-36, ST-36) significantly reduced abdominal withdrawal reflex (AWR) scores in NMD rats but not in age-matched healthy control rats. In addition, EA treatment hyperpolarized resting membrane potentials, increased the rheobase and reduced the numbers of action potentials evoked by 2 and 3 times rheobase current stimulation of dorsal root ganglion (DRG) neurons innervating the colon. NMD markedly enhanced expression of TRPV1 in colon related DRGs while EA treatment drastically suppressed the expression of TRPV1 in DRGs of NMD rats. These data suggest that EA treatment produced an analgesic effect, which might be mediated at least in a part by suppression of TRPV1 expression and by inhibition of neuronal excitability of primary sensory neurons in rats with chronic visceral pain.
Highlights
Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, featured by chronic visceral hypersensitivity (CVH) and altered bowel movement
We have previously reported that EA treatment significantly inhibited the neuronal excitability of dorsal root ganglion (DRG) neurons and attenuated the CVH in a rat model of IBS induced by neonatal colonic inflammation [5]
Our results indicate that neonatal maternal deprivation (NMD)-induced visceral hypersensitivity is likely mediated by upregulation of TRPV1 expression and an increase of cell excitability in DRG neurons, and that EA treatment relieves visceral hypersensitivity through the inhibition of TRPV1 upregulation and the reduction of excitability of DRG neurons innervating the colon in this setting
Summary
Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, featured by chronic visceral hypersensitivity (CVH) and altered bowel movement. The treatment of CVH in IBS patients remains challenging for the clinicians. Both acupuncture and electroacupuncture (EA) have been applied in treating many diseases including chronic pain for the past several decades [1]-[3]. It has been demonstrated that EA treatment produces a significant improvement both in general well-being and in symptoms of chronic visceral hypersensitivity [4]. These data suggest that EA could be a promising method to treat chronic pain in patients, scientific evidence is very little and frequently contradictory. Further observations of the efficacy and the underlying mechanisms of EA are definitely needed
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