CARDIOVASCULAR-RESPONSES TO GASTRIC HYPOOSMOLAR STIMULATION IN ANESTHETIZED DOGS

We compared the cardiovascular response to the gastric infusion of dis tilled water (DI) with that to the gastric infusion of 0.9% saline (SI ) and gastric ballooning with 37-degrees-C water (BA) through a gastri c fistula in splenectomized mongrel dogs (n = 7). DI, and SI amounting to 5% of body wt and the same volume of water were infused in approxi mately 20 s through the tube and responses in mean arterial pressure ( MAP), CVP, heart rate (HR), and intra-esophageal pressure (EP) were mo nitored continuously. After DI, SI, and BA, the measured variables sho wed significant increases and attained maximal increases at about 2 mi n after the treatments. After DI, the maximum elevation in MAP was 21. 3 +/- 1.9 mmHg and 2 times higher than in SI and BA. The corresponding value in CVP was 5.0 +/- 0.3 mmHg and 2-3 times higher than with SI a nd BA, and HR increased by 26.1 +/- 3.0 beats/min showing 3 to 6 times larger increases compared with SI and BA. These gastro-cardiovascular reflexes were abolished after subdiaphragmatic truncal vagotomy. Thes e findings suggest that both the mechanical and osmotic stimuli to the stomach induce cardiovascular reflexes and that the vagus is involved in the reflex.