Social Instability Stress Research Articles

P49 Novel marine compounds — antitumor or genotoxic: Role of endpoint biomarkers

We investigated the immediate and lasting effect of social instability stress in adolescence [SS: daily 1 h isolation and change of cage partner postnatal days (P) 30–45] on cell proliferation in the hippocampus and on spatial memory using an object spatial location (SL) test. Female rats were treated with bromodeoxyuridine (BrdU) P43–45, and on P49, SS had reduced cell hippocampal cell proliferation/survival compared to controls as indicated by BrdU immunoreactive cell counts (p = 0.009), and did not differ in Ki67 immunoreactive cell counts (p = 0.15) from CTL. A separate group of SS and CTL rats were tested at P47 and P48, and again at P72 and P73 on the SL test using 1 and 8 h retention intervals. SS and CTL females did not differ in adolescence, but CTL had better memory than SS as adults (p = 0.03). The better memory performance of CTL rats is not due to differential investigation of objects during the familiarization pre-tests or by differential locomotor activity. The lasting memory reduction and reduced cell proliferation/survival in SS rats is consistent with the hypothesis that ongoing development of the hippocampus renders the adolescent particularly vulnerable to chronic social stress.

Social stress does not interact with paradoxical sleep deprivation-induced memory impairment

Extensive evidence has linked both paradoxical sleep (PS) and stress to memory processing. The purpose of the present study was to examine the effect of social instability stress on memory and to verify whether this stress interferes with the amnesic effect of PS deprivation using the modified multiple platform method. In addition to the PS-deprived group (put onto narrow platforms inside the deprivation tanks) two control groups were used: one of them remained in its home-cages and the other was placed inside the deprivation tanks, onto a grid that contained large platforms on it. All groups were subdivided in socially stable and unstable conditions. Immediately after 96 h of sleep deprivation, the animals were trained in three different memory tasks: inhibitory avoidance, classical fear conditioning to a discrete stimulus and contextual fear conditioning. Twenty-four hours after training, the animals were tested in order to assess task acquisition. The results showed that social instability did not impair the performance of animals nor interacted with PS deprivation in any of the tasks. Grid control animals presented a selective impairment in the inhibitory avoidance task and contextual, but not in the classical, fear conditioning task, compared to cage control rats. This finding could be due to the stress to which grid control animals were exposed (humidity and luminosity) during the manipulation period. PS-deprived animals exhibited poorer performance than the other groups in all tasks. As they also showed an increased threshold to shock-induced vocalisation, but not to flinch response, it is not possible to completely rule out a decreased response to noxious stimulation as a contributing factor for the present results with PS deprivation.