Development of a new rabbit ear model for the longitudinal study of digital pathophysiology.

A rabbit ear model has been developed in which arterial pressure, auricular blood flow conductance, and microvascular perfusion can be followed continuously in conscious animals. Conductance is measured with a transit-time flow probe placed around the auricular artery, arterial pressure is measured with an abdominal aortic catheter, and cutaneous microvascular perfusion is assessed using laser Doppler fluxmetry. Placement of a femoral vein catheter permits administration of vasoactive substances. To date, rabbits have been instrumented for 90 days or longer. Auricular and abdominal arterial pressures were equal, permitting the calculation of auricular artery conductance. Microvascular perfusion as measured by laser Doppler fluxmetry followed changes in overall blood flow. The presence of postsynaptic alpha 2-receptors was confirmed by determining auricular conductance before and after the administration of intravenous alpha-agonists. The development of this unique model will help to advance the understanding of the pathophysiology of human digital thermoregulatory vascular abnormalities.