Splenic and renal sympathetic responses to stimulation of splenic receptors in cats.

The effect of selective stimulation of splenic receptors on reflex responses of splenic and renal efferent nerves was studied in anesthetized, vagotomized, sinoaortic denervated cats. The following substances were injected into the artery or vein of vascularly isolated spleens: warm physiological saline (congestion), capsaicin (CAPS), bradykinin (BK), and norepinephrine (NE). Splenic congestion increased efferent activity of splenic and renal nerves, splenic venous pressure, systemic arterial pressure, and heart rate. CAPS and BK elicited responses similar to those produced by congestion but caused greater excitation of splenic than renal nerves. Reflex responses were eliminated by section of splenic nerves. Injection of NE increased splenic venous pressure but did not elicit reflex responses. Finally, in contrast to a previous report light- and electron-microscopic examination of splenic nerves revealed myelinated, as well as unmyelinated, fibers. These results have demonstrated that activation of splenic receptors elicits reflex cardiovascular responses and excitation of splenic and renal efferent nerves, contraction of the spleen does not produce reflex responses, the adequate stimulus for reflex responses is stretch of vessels and possibly capsule, and splenic receptors play a role in the reflex control of circulation.