Cardiovascular reflexes resulting from capsaicin-stimulated gastric receptors in anesthetized dogs

To determine whether significant cardiovascular reflexes can be generated from gastric receptor stimulation, we developed an autoperfused canine stomach preparation from a dog anesthetized with α-chloralose so that capsaicin, a C fiber agonist, could be injected into the left gastroepiploic artery (ia) supplying the greater curvature of the stomach. Control injections were made into the inferior vena cava (IVC) to determine capsaicin's effects on areas downstream from the stomach. Significant cardiovascular reflexes were obtained in 37 of 42 dogs after ia injection and in 26 of 26 dogs after IVC injection. Capsaicin (25-500 μg) caused significant increases in systolic blood pressure (SBP) (15%), heart rate (HR) (4%), contractility (maximal dP/dt) (19%), and systemic vascular resistance (SVR) (18%), whereas there were no changes in left ventricular end-diastolic pressure (LVEDP) or aortic flow (AF). On the other hand, downstream IVC capsaicin injections caused significant decreases in SBP (28%), HR (34%), dP/dt (33%), and AF (41%), but no change in SVR or LVEDP. The dP/dt response to ia injection continued to occur after overdrive right atrial pacing. However, the responses of pressure, rate, and dP/dt were diminished to a large extent by diaphragmatic celiac nerve section and to a smaller extent by diaphragmatic vagus nerve section. We conclude that these results demonstrate that capsaicin, a potent C-fiber agonist, can stimulate gastric or perigastric receptors to induce a significant activation of the cardiovascular system. Thus, the potential of the stomach to function as a reflexogenic organ which regulates the cardiovascular system has been demonstrated.