シロネズミの慢性ストレスに及ぼす対応反応の効果

抄録

It is well known that stress-induced physiological changes, such as gatrointestinal ulcers or essential hypertension, are innate reactions to chronic fear. But from the point of view of organic adaptation, any learning of the abersive situation that affects the strength or duration of the fear elicited may be expected to influence the physiological simptoms of stress. A psychological factor of this type of learning depends on whether or not the animal can "think" of a way to cope with the stress when the stressor arrives.The present study was conducted to determine the effects of coping response on chronic stress in the rat in a free-operant avoidance situation(R-S interval, 200 sec., S-S interval, 0.4 sec., shock intensity, 2.25 ma. mean) when measured by stomach lesions. The matched quartet design was employed. Each quartet consisted of an experimental animal (N=11) which could avoid or escape shocks by its flapper-pushing rsponse, a yoked animal (N=11) which received the same intensity and duration of shocks as the expeimental animal but which could not avoid or escape shocks, a nonshock control animal (N=11) which was never shocked throughout the experiment, and a home-cage control animal (N=11) which remained in his individual cage in the rat colony room. Avoidance-escape stress sessions lasting 23 hrs. followed by 1 hr. feeding-rest periods were repeated for 7 days. Flapper-pushing rate, body weight, and food and water intake were recorded daily. Gastric incidence was noted at the termination of the eight experimental day. Results of teh present study showed that the yoked group developed more severe gastric lesions than experimental, nonshock, or home-cage control group and also confirmed findings of previous acute stress experiments by indicating that subjects which could not control shock were more stressed than subjects which could. Through the ezperimental and yoked groups did not differ in body weight loss during the chronic stress session, both the nonshock and home-cage control groups differed significantly from the other two shocked grouls. The experimental group ate and drank somewhat more than the yoked group. The home-cage control group showed the most food an water intake, All experimental group subjects made more flapper pushes than in all matched yoked or nonshock subjects, as would be expected. Response rates were similar either eleven triplets.These results were predicted by Weiss' ulcer-prediction model which related ulceration to certain psychological (or behavioral) variables. Also an explanation for the atypical "exective" monkey pehnomenon was attained.