Roles of putative neurotransmitters in the regulation of gastric and intestinal slow waves in conscious dogs.
OBJECTIVE
Slow waves play an important role in controlling the frequency and propagation of gastrointestinal contractions. However, mechanisms involved in the modulation of slow wave activity in vivo are still unclear. In this study, the roles of different neurotransmitters in the regulation of gastrointestinal slow waves were investigated in conscious dogs.


METHODS
Female dogs implanted with electrodes in the stomach and the small bowel were used in a seven-session study. Gastrointestinal myoelectrical activity was recorded at baseline and after i.v. saline, atropine, atropine methyl nitrate, guanethidine, Nomega-nitro-L-arginine (L-NNA), ondansetron or naloxone.


RESULTS
Both atropine and atropine methyl nitrate induced tachygastria, bradygastria and arrhythmia. No difference was noted in the effects between atropine and atropine methyl nitrate. L-NNA increased the dominant frequency of small-intestinal slow waves but had no effect on gastric slow waves. Guanethidine, ondansetron and naloxone did not affect the dominant frequency, power or percentage of normal gastrointestinal slow waves.


CONCLUSIONS
Acetylcholine acting at muscarinic receptors seems to play an important role in the regulation of gastric slow waves. Nitric oxide may play a role in modulating intestinal slow waves but not gastric slow waves. Sympathetic pathways, 5-HT(3) receptors and opioid receptors (especially micro-opioid receptors) do not play a role in the regulation of gastric or intestinal slow waves under normal physiological conditions.
Liu
Shi
S
Division of Gastroenterology, University of Texas Medical Branch, Galveston, Texas, USA.
Xu
Junying
J
Chen
Jiande Dz
JDz
D000818:Animals; D003243:Consciousness; D004285:Dogs; D005260:Female; D005769:Gastrointestinal Motility / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors / Q000502:physiology*
D018377:Neurotransmitter Agents