Neural mechanisms involved in the delay of gastric emptying and gastrointestinal transit of liquid after thoracic spinal cord transection in awake rats.

Spinal cord transection (SCT) delays gastric emptying (GE), and intestinal and gastrointestinal (GI) transit of liquid in awake rats. This study evaluates the neural mechanisms involved in this phenomenon. Male Wistar rats (N = 147) were fasted for 16 h and had the left jugular vein cannulated followed by laminectomy or laminectomy + complete SCT between T4 and T5 vertebrae. The next day, a test meal (1.5 ml of a phenol red solution, 0.5 mg/ml in 5% glucose) was administered by gavage feeding and 10 min later cervical dislocation was performed. Dye recovery in the stomach, and proximal, mid and distal small intestine was determined by spectrophotometry. SCT inhibited GE and GI transit since it increased gastric recovery by 71.3% and decreased mid small intestine recovery by 100% (P < 0.05). Subdiaphragmatic vagotomy, celiac ganglionectomy + section of the splanchnic nerves, i.v. hexamethonium (20 mg/kg) or yohimbine (3 mg/kg) prevented the development of the SCT effect on GE and GI transit. Pretreatment with i.v. naloxone (2 mg/kg), L-NAME (3 mg/kg) or propranolol (2 mg/kg) was ineffective. Bilateral adrenalectomy or guanethidine (10 mg/kg) increased the magnitude of the GE inhibition, while i.v. prazosin (1 mg/kg) or atropine (0.5 mg/kg) decreased the magnitude but did not abolish the GE inhibition. In summary, the inhibition of GI motility observed 1 day after thoracic SCT in awake rats seems to involve vagal and possibly splanchnic pathways.

Complete cervical or thoracic spinal cord transections delay gastric emptying and gastrointestinal transit of liquid in awake rats.

STUDY DESIGN: To determine the changes on gastric emptying and gastrointestinal transit of liquid throughout the first week after spinal cord transection (SCT) in rats. METHODS: Male Wistar rats (n=121) were fasted for 16 h and a complete SCT or laminectomy was performed between C7 and T1 (cervical group) or between T4 and T5 (thoracic group). Dye recovery in the stomach, proximal, mid and distal small intestine was determined 30 min, 6 h, 1, 3 or 7 days after surgery. The test meal (1.5 ml of a phenol red solution, 0.5 mg/ml in 5% glucose) was intragastrically administered and the animals sacrificed by cervical dislocation 10 min later. RESULTS: Cervical SCT increased dye recovery in the stomach (P<0.05) by 70.1, 78.7, 34.2, 41.3 and 50.9% while it decreased recovery in the mid small intestine (P<0.05) by 87.1, 85.1, 74.8, 59.5 and 80.1%, respectively 30 min, 6 h, 1, 3 and 7 days after SCT. Thoracic SCT increased gastric recovery (P<0.05) by 43.5, 67.6, 51.2, 75.4 and 38. 9% while it decreased recovery in the mid small intestine (P<0.05) by 100, 100, 45.6, 100 and 66.6%, respectively 30 min, 6 h, 1, 3 and 7 days after SCT. A separate group was submitted to laminectomy+bilateral sciatic nerve transection (paraplegic sham). Gastric emptying and gastrointestinal transit were not inhibited in this group. CONCLUSION: In summary, gastric emptying and gastrointestinal transit of liquid are inhibited throughout the first week after high SCT in awake rats.

Neural mechanisms involved in the delay of gastric emptying of liquid elicited by acute blood volume expansion in awake rats.

We have previously reported that acute blood volume expansion in awake rats delays the gastric emptying of a liquid meal, using the phenol red method. In this study we attempted to investigate the neural mechanisms involved in this phenomenon. Blood volume expansion, due to Ringer-bicarbonate infusion up to a volume equivalent to 5% of body weight, decreased the gastric emptying of a liquid meal by half (38.2 +/- 1.8 vs 18.7 +/- 3.2%, P < 0.05). The blood volume expansion effect on gastric emptying of liquid was prevented by separate pretreatments, consisting of subdiaphragmatic vagotomy or i.v. injection of hexamethonium (20 mg kg-1) or yohimbine (3 mg kg-1). Intravenous injection of atropine (0.5 mg kg-1), guanethidine (10 mg kg-1), L-NAME (3 mg kg-1), prazosin (1 mg kg-1) or propranolol (2 mg kg-1) did not prevent the blood volume expansion effect on gastric emptying. Bilateral adrenalectomy or coeliac ganglionectomy were also ineffective. The results indicate that blood volume expansion decreases gastric emptying of liquid through vagal-dependent pathways, sensitive to hexamethonium and yohimbine. Evidence for the participation of the peripheral sympathetic nervous system was not found.