In this study, we investigated the effects of acute and chronic immobilization stress on the Zn, Cu, and Fe levels of the temporal lobe, brain stem, spleen, and liver tissues in rats. The animals in the acute stress group were put in the cages, one time only for 120 min. For the chronic stress groups (2h and 4h), the rats were kept in the cages daily for 2 and 4 h, respectively, for 5 consecutive days. Controls and immobilized rats were decapitated, and then tissue samples were taken. Zn, Cu, and Fe levels in the temporal lobe, brain stem, spleen, and liver were measured by flame atomic absorption spectrophotometer. Our results showed that acute immobilization stress causes endogenous Zn and Cu release from the brain tissues. In the 2h chronic stress group, Fe levels markedly increase in the temporal lobe and brain stem whereas they decrease in the spleen and liver. In the 4h chronic stress group, Fe levels increase in the temporal lobe and brain stem while Zn and Cu levels increase in the spleen and liver. In the acute and chronic immobilization stress groups, mobilization of Zn and Cu can be related to the induction of metallothionein (MT) in the liver and spleen but not in the brain. On the other hand, excess Fe in the temporal lobe and brain stem causes us to believe think that the brain iron transport proteins may be involved, and enhanced, by immobilization stress.

In this study we aim to discuss the relationship between stress and learning and emotionality in an experimental model using two different stress conditions: acute stress (single restraint stress for 20 min) and repeated severe stress (6-h daily restraint for 21 days). We studied the effects of tianeptine, which has been suggested to have anxiolytic and cognition-enhancing effects under stressful conditions. After acute stress, the increase in the duration of immobility (F = 5.753 and 3.664) in the open field and holeboard tests and the decrease in rearing (F = 3.891) in the holeboard test were significant when compared to controls (P < 0.05). Results for repeated severe stress showed that in both the open field and holeboard tests the decrease in rearing (F = 4.494 and 4.530, respectively), increase in the duration of immobility (F = 6.069 and 4.742, respectively) and decrease in head dips (F = 4.938) in the holeboard test were statistically significant (P < 0.05). The group pretreated with tianeptine showed no significant difference from controls for either acute or repeated severe stress conditions. In the Morris water maze test, acute stress led to a prolongation of average escape latency, which indicated a spatial learning deficit. Treatment with tianeptine prior to acute stress prevented this spatial deficit. Repeated severe stress also led to spatial learning deficits in rats, but this deficit was not prevented by treatment with tianeptine. Our study demonstrates that pretreatment with tianeptine had different effects on stress-induced spatial learning deficits under acute and repeated stress conditions, while the effects on emotionality and anxiety-like behavior were similar. The mechanisms implicated in stress-induced emotional and memory deficits will be discussed.

TurkeyCentral administration of neuropeptide Y (NPY) produces anxiolytic-like behavioral responses in the conflict test, elevated plus maze, fear-potentiated startle paradigm, and in the chronic immobilization stress. Exogenously administrated NPY also protects against the anxiogenic effects of corticotropin-releasing factor. In the present study, we aimed to determine the effects of centrally administered NPY on the trace element disturbances in brain tissues (frontal and temporal lobes and brain stem) and the other major organs including liver, spleen (zinc [Zn]-, copper [Cu]-, and iron-rich tissues), kidney, and stomach in chronically immobilized rats. The immobilization stress was performed in special cages in which the animals were not able to move. The rats in chronic stress and chronic stress + NPY groups were kept in the cages daily for 7 min for 15 consecutive days. Intracerebroventricular (ICV) cannulas were placed to the right lateral ventricles of the rats by using stereotaxic method. In the control and chronic stress groups, 5 lL of saline (NaCl 0.9%), and in the chronic stress + NPY group, 8 lg NPY/5 lL saline solutions, were administered into the brain via ICV cannula, respectively. Controls and immobilized rats were decapitated 30 min after the injections were over and samples of tissue were taken. Zn, Cu, and iron levels of the frontal lobe, temporal lobe, brain stem, liver, spleen, kidney, and stomach were determined by flame atomic absorption spectrophotometer. Zn and Cu levels were significantly increased in the frontal lobe, temporal lobe, and brain stem in response to chronic immobilization stress daily for 7 min for 15 consecutive days. The administration of NPY inhibited the elevation of Zn in these three parts of brain but did not affect the elevation of Cu in the frontal lobe and brain stem. levels of frontal, temporal lobes, and brain stem may be related to induction of MT-I mRNA expression by chronic immobilization stress, and NPY may affect this induction of MT-I, altering corticotropin-releasing factor release in the stress conditions.

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Our results revealed that during the competitive interaction of these two peptides, anxiogenic CART peptide suppressed the anxiolytic effects of NPY.