Cardiorespiratory responses to chemical activation of right ventricular receptors

Previous reports have shown that activation of left ventricular receptors with sympathetic afferents elicits increases in respiratory output and arterial pressure. The purpose of the present study was to determine whether similar responses are produced by chemical activation of epicardial receptors in the right ventricle. Receptors were stimulated by applying either capsaicin (10 micrograms) or bradykinin (500 ng) to the epicardial surface of the right ventricle in anesthetized cats. Application of either chemical evoked an increase in respiratory output (phrenic nerve activity), a decrease in heart rate, and a nonsignificant increase in arterial pressure in intact cats. However, capsaicin and bradykinin produced significant increases in arterial pressure, heart rate, and respiratory output after bilateral cervical vagotomy. In contrast, a fall in both heart rate and arterial pressure with only small increases in respiratory output were evoked after bilateral removal of the stellate ganglia in cats with intact vagi. Only small responses to the chemical stimulation of right ventricular receptors persisted after combined vagotomy and stellate ganglionectomy. These findings suggest that 1) activation of epicardial receptors with sympathetic afferents originating in the right ventricle causes an increase in cardiorespiratory function, and 2) activation of right ventricular receptors with vagal afferents produces decreases in heart rate and arterial pressure.