AJP - Heart and Circulatory Physiology, Vol 242, Issue 6 955-H960, Copyright © 1982 by American Physiological Society
Reflex cardiovascular depression induced by capsaicin injection into canine liver
J. H. Ashton, G. A. Iwamoto, J. C. Longhurst and J. H. Mitchell
Capsaicin was injected into the portal circulation of 29 dogs after a blood
delay pathway was constructed between the liver and right heart, through
which capsaicin-contaminated blood could be replaced while systemic
hemodynamics were maintained constant. Capsaicin (500 micrograms) rapidly
decreased left ventricular systolic pressure (-10%), mean arterial pressure
(-12%), heart rate (-4%), renal vascular resistance (-7%), maximal rate of
left ventricular pressure rise (dP/dtmax) (-12%), and dP/dt at 25 mmHg
developed left ventricular pressure (-15%) in animals with paced hearts.
Left ventricular end-diastolic pressure did not change. Vagus nerve
interruption at the level of the diaphragm did not alter hemodynamic
changes occurring during capsaicin injections, but anterior hepatic nerve
interruption eliminated the changes, suggesting that the cardiovascular
responses were reflex in origin and that the principal afferent pathway
traverses the hepatic nerve. This study demonstrates that activation of
afferent fiber receptors within the liver tissue can contribute to neural
regulation of the cardiovascular system, but the natural stimulus for these
receptors is not known.
