Problems in the interpretation of blood pressure changes seen in rats fed a breakfast cereal

Systolic blood pressures were measured on the same animals by direct and indirect methods. A tail cuff was used for the indirect measurements, and the direct measurements were obtained with a strain gauge after a needle was inserted into a major artery. Good agreement was found between normal values and elevated pressures produced by norepinephrine, but gross differences were observed in a nutritional experiment in which oatmeal was fed. Credibility requires that blood pressure changes be demonstrated by direct as well as by indirect measurements.