The effects of differential psychological stress on plasma cholesterol levels in rats.

The plasma cholesterol concentrations of rats receiving either lever-press escape or avoidance training, exposure to unpredictable, uncontrollable grid shocks using a yoked procedure, or no shocks, were compared in two experiments. All were fed a cholesterol-supplemented diet prior to and during the 30 days of exposure to these differing stress treatments. The results of both experiments showed that yoked groups had higher terminal levels of cholesterol than their experimental counterparts in the escape or avoidance group even though they received the same amounts of aversive stimulation and ate the same amounts of the diet. Both were higher than the nonshocked groups when the amount of food intake for all was matched in Experiment 2. The type of level-press training had no effect.