L-glutamate microinjection into DMV can both increase and decrease gastric volume in mice

Abstract

into the skin and underlying muscles on the hind limb (ST-36) was manually twisted left and right once every second fbr 30 seconds Results: Two types of fasting gastric motor patterns were observed in conscious rats, Of 25 rats studied, 15 rats (type A; 60 %) showed no cyclic groupings of strong contractions, whik 10 rats (type B; 40 %) showed cyclic groupinga of strong contractions similar to the phase llI contractions observed in the humans and dogs in 11 (73 %) of 15 type A rats, acupuncture on the hind limb induced phase IlI-like contractions that lasted for more than 3 hrs. The amplitude of gastric contractions was significantly increased by acupuncture to 213.8 + A20.1% of controls (M +/-SE, n = 6, p<0.01). The motility index of phase llI-like contractions induced by' acupuncture in type A rats was signdlcantly higher than that of type B rats (81.2 +/3.3 vs 42.1 +A1.5 g min, n = 6, p<0.01). In contrast, acupuncture on the back had no effects on gastric contractions. Acupunctul~ failed to induce a W phase Ill-like contractions in type A rats, once treated with atropine (50 micro g/kg, s.c.), hexamethoninm (20 mg/kg, s.c.) and snbdiaphragmatic bilateral vagotomy Pretreatment wqth naloxone (5 mg/kg, i.p.) significantly' shortened the duration of pha~ lIIdike contractions induced by' acupuncture from 3.68 +/-0.10 to 1.06 +/0.11 hr (n=3 , P<0.01) In 6 of 10 type B rats, acupuncture on the hind limb significamly suppressed the atnplitude of phase Ill-like contractions to 67.4 +/-10.2 % of controls (n = 4, p<005) . Among 10 of type B rats studied, none of them showed increased phase Ill contractions in response to acupunctm'e. Conclusions: Acupuncture on the hind limb induces dual eftects, either stimulato Dor inhibitoD', on gastric motility in conscious rats. The stimulator}' effects are mediated via vagal cholinergic and opioid pathway. Opioid pathway may contribute to the long-lasting stimulatory effects ot acupuncture on gastric motility.