Elevation of plasma renin activity during avoidance performance in baboons

The effect of a 3-h Sidman avoidance operant conditioning schedule (liver pressing to avoid an electric shock) on plasma renin activity and renin substrate concentration was examined in baboons (Papio cynocephalus). Plasma samples were drawn over a 24-h period on both the control and test days, and the avoidance session was presented on the morning of the test day. Plasma renin activity was significantly higher on the test day than at the corresponding hours of the control day at 1, 2, and 3 h after onset of the avoidance test and 30 min after its termination (P = .032). The magnitude of the increase in plasma renin activity was not correlated with either the rate of lever pressing or the number of shocks received. Renin substrate concentration was not changed during or after the avoidance session. These data demostrate that plasma renin activity can be increased by a psychological stimulus.