Cardiovascular Function During Pre‐Avoidance, Avoidance, and Post‐Avoidance in Dogs

Four dugs, implanted with aortic blood flow probes and catheters, were trained to press a panel during signalled shock avoidance and switched to an hour of Sidman avoidance per day for a minimum of 10 days, Cardiovascular function (heart rate=HR; stroke volume=SV: blood pressure = BP; cardiac output = CO; total peripheral resistance =TPR; and maximum aortic (dp/dt) was determined during the hour preceding avoidance, during avoidance, and during a 10 min post‐avoidance period, Data from 4 dogs were analyzed. Two behaviorally reactive dogs showed elevated BP due to increased TPR during pre‐avoidance and increased CO during avoidance. Increases in SV. HR. and dp/dt, most pronounced at the beginning of avoidance, suggest a change in left ventricular function. Intercorrelations between HR and dp/dt revealed apparent influences of the Frank‐Starting mechanism during pre‐avoidance, and cardiac contractility during avoidance. The 2 remaining animals were less reactive and showed only some of the patterns consistently seen in the 2 more reactive dogs. The data were discussed in terms, of obtaining a model for early stages of human hypertension.