Relation of cardiovascular changes in fighting to emotion and exercise.

1. To obtain evidence on the relative importance of exercise and emotion in the cardiovascular changes of fighting in the cat, the changes during fighting were compared with changes during a mild non-emotional exercise (walking on a treadmill at low speed), and during confrontation without fighting (preparation for fighting), an emotional condition accompanied by no or very little motor activity.2. The direction of change of all variables we measured, iliac and mesenteric flows and conductances, total peripheral conductance, heart rate, cardiac output and blood pressure, was similar in both fighting and exercise.3. Some of the cardiovascular manifestations of preparation for fighting were very different from those of motor activity. These were iliac vasoconstriction, a fall in cardiac output, and often a strong bradycardia, all of these changes being in the opposite direction to changes during exercise and fighting.4. It is suggested that the changes during preparation for fighting represent the cardiovascular manifestations of an emotional state, and that during fighting these manifestations are superseded and masked by changes due to motor activity.