PERSISTENT PLASMA-CHOLESTEROL ELEVATIONS ARE PRODUCED BY ONE OR 3 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 s tressor protocols. We report on two studies in which we measured plasm a CHOL 22-h poststressor in rats fed Purina Laboratory Rodent Chow and exposed to 3 (3-day) or 1 (1-day) daily stressor sessions [40, 2 mA t ailshocks]. In the first study, both the 3-day and 1-day groups exhibi ted moderately elevated morning plasma CHOL 22-h poststressor compared to nonshocked controls. Along with the groups in the first study, a s econd study included a restricted food control, rats transferred to th e stressor environment, and rats simply transferred to an adjacent roo m. Neither restricted feeding nor the room transfers had an effect on morning plasma CHOL. However, the 3-day and 1-day groups again exhibit ed moderately elevated CHOL. Previous reports did not find elevated pl asma 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 relativel y slow development of plasma CHOL elevations may be related to the tim e course of stressor-induced thyroid suppression.