[Stress-induced blood protein and blood lipid changes and their dependence on learning and conditioning]

Rats were subjected to two kinds of stress and consequent changes in blood protein and lipids were investigated. Furthermore, an attempt was made to ascertain whether or not increases or decreases in these blood parameters were reproducible by conditioning. In the first experiment animals were subjected to stress in a modified running wheel (Noble Collip drum). A series of 10 conditional stimuli (light-sound combined) was delivered together with the stress-producing stimulus. After the first exposure to stress a relative alpha1-globulin increase was observed. After 10 stress exposures the hitherto neutral stimulus alone produced a conditioned increase in the alpha1-globulin fraction. The gamma-globulin values were decreased after the first exposure to stress, but increased after 10 stress exposures. This increase could also be conditioned. In the second experiment "white noise" stress was used (110 dB). The conditional stimulus was light. After short exposure to the stress-inducing stimulus, the gamma-globulins showed a slight drop and remained thus during the whole experiment. The analysis of blood lipids showed increased stress values for alpha-lipoprotiens and reduced values for beta-fractions. Cholesterol and triglycerides reacted like the beta-lipoproteins. The total blood lipid content was, however, increased. The conditioned increase in alpha-lipoproteins and total lipids was statisticallysignigicant. It is noteworthy that the conditioned alpha-lipoprotein levels shoeed significant differences between experimental and control groups. The conditioned stress increased the levels of cholesterol and triglycerides, whereas under real stress conditions decreases were found. Research on "conditioned stress" could beof improtance in regard to clinical aspects of coronary heart disease.