Atrial stretch delays gastric emptying of liquids in awake rats

Aims We previously reported that mechanical atrial stretch (AS) by balloon distention increased gastric tonus in anesthetized rats. The present study evaluated the effect of AS on the gastric emptying of a liquid test meal in awake rats and its underlying neural mechanisms. Main methods Anesthetized male rats received a balloon catheter into the right atrium and a gastrostomy cannula. The next day, mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), and cardiac output (CO) were continuously monitored. After the first 20 min of monitoring (basal interval), the balloon was either distended or not (control) with 30, 50, or 70 μl saline for 5 min. Fifteen minutes later, the rats received the test meal (glucose solution with phenol red), and fractional gastric dye retention was determined 10, 20, or 30 min later. Key findings Heart rate and CVP values were transiently increased by 50 or 70 μl AS but not 30 μl AS, whereas gastric emptying was slower after 30, 50, or 70 μl AS than after sham distention. Subdiaphragmatic vagotomy or splanchnicotomy + celiac ganglionectomy and capsaicin, ondansetron, hexamethonium, L-NAME, and glibenclamide treatment prevented the AS-induced delay in gastric emptying, whereas atropine and guanethidine treatment failed to prevent it. Significance Atrial stretch inhibited the gastric emptying of liquid via non-adrenergic and non-cholinergic pathways that activate nitric oxide-K + ATP channels.