We studied whether physiological concentration of short-chain fatty acids (SCFAs) affects colonic transit and colonic motility in conscious rats. Intraluminal administration of SCFAs (100-200 mM) into the proximal colon significantly accelerated colonic transit. The stimulatory effect of SCFAs on colonic transit was abolished by perivagal capsaicin treatment, atropine, hexamethonium, and vagotomy, but not by guanethidine. The stimulatory effect of SCFAs on colonic transit was also abolished by intraluminal pretreatment with lidocaine and a 5-hydroxytryptamine (HT)(3) receptor antagonist. Intraluminal administration of SCFAs provoked contractions at the proximal colon, which migrated to the mid- and distal colon. SCFAs caused a significant increase in the luminal concentration of 5-HT of the vascularly isolated and luminally perfused rat colon ex vivo. It is suggested that the release of 5-HT from enterochromaffin cells in response to SCFAs stimulates 5-HT(3) receptors located on the vagal sensory fibers. The sensory information is transferred to the vagal efferent and stimulates the release of acetylcholine from the colonic myenteric plexus, resulting in muscle contraction.

. Dual effects of acupuncture on gastric motility in conscious rats. Am J Physiol Regul Integr Comp Physiol 285: R862-R872, 2003; 10.1152/ ajpregu.00715.2002The effects of manual acupuncture on gastric motility were investigated in 35 conscious rats implanted with a strain gauge transducer. Twenty (57.1%) rats showed no cyclic groupings of strong contractions (type A), whereas 15 (42.9%) rats showed the phase III-like contractions of the migrating motor complex (type B) in the fasting gastric motility. Acupuncture at the stomach (ST)-36 (Zusanli), but not on the back [Weishu, bladder (BL)-21], increased the peak amplitude of contractions to 172.4 Ϯ 25.6% of basal in the type A rats (n ϭ 20, P Ͻ 0.05). On the other hand, the motility index for 60 min after the acupuncture was not affected by the acupuncture in this group. On the contrary, acupuncture decreased the peak amplitude and motility index to 72.9 Ϯ 14.0% and 73.6 Ϯ 16.2% in the type B rats (n ϭ 15, P Ͻ 0.05), respectively. The stimulatory and inhibitory effects of acupuncture observed in each type were reproducible on the separate days. In 70% of type A rats, acupuncture induced strong phase III-like contractions lasting for over 3 h that were abolished by atropine, hexamethonium, atropine methyl bromide, and vagotomy. Naloxone significantly shortened the duration of the stimulatory effects from 3.52 Ϯ 0.21 to 1.02 Ϯ 0.15 h (n ϭ 3, P Ͻ 0.05). These results suggest that acupuncture at ST-36 induces dual effects, either stimulatory or inhibitory, on gastric motility. The stimulatory effects are mediated in part via vagal efferent and opioid pathways. vagal nerve; migrating motor complex; stomach-36; opioid ACUPUNCTURE HAS BEEN USED empirically in clinical practice in China for several millennia (59). In November 1997, the National Institutes of Health conducted a consensus conference regarding acupuncture and concluded that acupuncture is an effective treatment for several medical conditions. Although a large number of previous clinical studies support the efficacy of acupuncture for treating gastrointestinal (GI) symptoms and/or diseases (9, 16), little is known about the underlying mechanism(s).It has been demonstrated that the somatosensory inputs from the skin and/or muscle are involved in the control of various autonomic functions (22,26). A series of investigations regarding somato-autonomic reflexes has also been carried out focusing on GI function. In some of those investigations, there is good evidence indicating the importance of cutaneo-sensory inputs in the autonomic control of GI motility. In anesthetized rats, for instance, it has been shown that the cutaneogastric reflexes mediate the inhibition and the stimulation of gastric motility via sympathetic and parasympathetic efferents, respectively (24,28,47). It was shown that the cutaneo-sensory stimulation induced by pinching abdominal skin of rats inhibits gastric motility by increasing sympathetic activity. On the other hand, cutaneo-sensory stimulation induced by pinching the hindlimb enh...

The results suggest that the longer and deeper abdominal incision more profoundly inhibits GI transit. The inhibitory effect of abdominal incision is mediated via the activation of the somatosympathetic reflex and alpha-2 adrenoceptors.