Effects of splanchnic nerve stimulation and of clonidine on gastric and duodenal HCO3- secretion in the anaesthetized cat.
Experiments were performed on chloralose-anaesthetized cats with ligated adrenals. The vagal and splanchnic nerves were cut and arranged for peripheral electric stimulation. The gastric lumen was perfused with isotonic saline and gastric H+ and HCO3- secretions were calculated from pH/pCO2 measurements in the perfusate. Gastric motility was recorded as changes in hydrostatic pressure in the perfusion circuit. Mucosal HCO3- secretion into the duodenum was monitored in situ by pH-stat titration. Vagal stimulation (10 Hz for 10 min) increased gastric and duodenal HCO3- secretions, as well as gastric motor activity and H+ secretion. Splanchnic nerve stimulation (10 Hz for 10 min) did not affect gastric H+ and HCO3- secretions, but tended to decrease gastric motor tone and basal duodenal HCO3- secretion. Splanchnic nerve stimulation simultaneously with vagal stimulation inhibited gastric contractions and the rise in gastric H+ and duodenal HCO3- secretions observed in response to vagal stimulation alone, but had little effect on the rise in gastric HCO3- secretion. However, such vago-splanchnic stimulation in the presence of the alpha 2-adrenoceptor blocker yohimbine induced gastric contractions, H+ secretory and duodenal HCO3- secretory responses with magnitudes similar to those induced by vagal stimulation alone, whereas the gastric HCO3- secretory response was larger than by vagal stimulation alone. The alpha 2-adrenoceptor agonist clonidine (50 micrograms kg-1 h-1, i.v.) inhibited the gastric contractions and increases in gastric and duodenal HCO3- secretion in response to vagal stimulation, but did not influence vagal stimulation of gastric H+ secretion. The results suggest the existence of a peripheral sympatho-inhibitory action on gastric and duodenal HCO3- secretion involving alpha 2-adrenoceptors. Also splanchnic neural stimulatory effects on gastric and duodenal HCO3- secretion may exist.
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002415:Cats; D003000:Clonidine / Q000494:pharmacology*; D004386:Duodenum / Q000187:drug effects*; D004558:Electric Stimulation; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D005769:Gastrointestinal Motility / Q000187:drug effects; D007419:Intestinal Secretions / Q000378:metabolism*; D008297:Male; D011224:Prazosin / Q000494:pharmacology; D013153:Splanchnic Nerves / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology
D001639:Bicarbonates; D015016:Yohimbine; D003000:Clonidine; D011224:Prazosin