Persistent plasma cholesterol elevations are produced by one or three stressor exposures in rats fed a normal laboratory diet

Typically, stress-related elevations in rat plasma cholesterol (CHOL) require preexposure to diets high in fats or cholesterol and lengthy stressor protocols. We report on two studies in which we measured plasma CHOL 22-h postressor in rats fed Purina Laboratory Rodent Chow and exposed to 3 (3-day) or 1 (1-day) daily stressor sessions [40, 2 mA tailshocks]. In the first study, both the 3-day and 1-day groups exhibited moderately elevated morning plasma CHOL 22-h poststressor compared to nonshocked controls. Along with the groups in the first study, a second study included a restricted food control, rats transferred to the stressor environment, and rats simply transferred to an adjacent room. Neither restricted feeding nor the room transfers had an effect on morning plasma CHOL. However, the 3-day and 1-day groups again exhibited moderately elevated CHOL. Previous reports did not find elevated plasma CHOL in rats given a single stressor exposure when sampled at the end of the stressor session. Thus, the persistently elevated morning CHOL exhibited by the 1-day group may develop over time. The relatively slow development of plasma CHOL elevations may be related to the time course of stressor-induced thyroid suppression.