The effect of early shock with or without a warning signal on adult behavior and susceptibility to stress-induced ulcers in the rat



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This study was undertaken to determine the effects of preweaning signalled and unsignalled shock on adult behavior and susceptibility to stress-induced gastric ulcers in albino rats. Fifty-four animals were separated into three groups of eighteen, receiving either signalled shock (SS1), unsignalled shock (US1), or no shock (NS1) for the first twenty-one days of life. At twenty-one days the subjects were weaned, weighed, and placed in individual cages; then, at fifty days were given emergence, open field, defecation and passive avoidance testing. The subjects were again tested at fifty-seven days, and then were placed in the adult stress situation which consisted on confinement in wire cages and exposure to signalled tail shock (SS2), unsignalled tall shock (US2), or no shock (NS2) for fortyeight hours. One-third of the subjects from each early treatment condition was placed in each late treatment group (therefore each early x late treatment condition contained six subjects). After adult treatment all subjects were weighed, killed, and examined for gastric ulcers. Additionally, two groups of six subjects each, one given US1-SS2 treatment and the other, SS1-US2 treatment, were run as above, but not given the intermediate tests on days fifty and fifty-seven, These groups were then compared to their appropriate, fully-treated counterparts to determine whether any residua of the intermediate behavioral testing would influence reactions to the stress situation. As it turned out, there were no such effects. The results demonstrated several differences among the groups of subjects. The NS1 subjects weighed less at weaning than did those given early shock, and at fiftyseven days still weighed least. They were also less active as determined by the emergence test, although the results of the open field test were inconclusive in this regard. They also had higher defecation scores than did the shocked groups. The SS2 animals were the least active overall, and this was. In part, reflected by their very low base performance on the passive avoidance task. The US1 subjects had significantly fewer and smaller ulcers than did either SS1 or NS1 subjects although there was no significant difference In amount of weight lost in response to later stress. There were no differences on any of the measures between US2 and SS2 animals, although this was attributed to procedural problems, and subjects In both groups developed more ulcers and lost more weight than did NS2 animals. These results are discussed in relationship to emotionality and activity measures, and the possible early effects of unpredictable stress.



Shock, Stress, Psychology, Ulcers, Rats--Behavior