Tehran University Medical Journal

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Background: Numerous evidences indicate that various environmental stresses during pregnancy affect physiological behavior of the offspring. This experimental study was designed to investigate the effect of noise stress during prenatal period of rats on spatial learning and memory and plasma corticostrone level in postnatal life.
Methods: Three groups of pregnant rats were given daily noise stress with durations of two and/ or four hours in last week of pregnancy period. The fourth group was left unstressed. The male offspring from the unstressed and different stressed groups were assigned as controls and stressed groups. The animals were introduced to a spatial task in Morris water maze 4 trials/day for five consecutive days. The probe test was performed on the 5^th day of the experiment. The delay in findings and the distance passed to locate the target platform were assessed as the spatial learning.
Results: Our results showed that prenatal exposure to noise stress for two and/ or four hours a day, leads to impaired acquisition of spatial learning in the postnatal animals. The plasma level of corticostrone in the two stressed groups of rats markedly matched with their behavioral function. Prenatal exposure to 1- hour noise stress revealed no effects on the offsprings' behavior and plasma corticostrone level.
Conclusion: Based on our study results, it seems that applied range of stress which is executed through the noise stress could increase the plasma corticostrone level and could decrease spatial learning and memory of adult male offspring.

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Background: Diabetes mellitus affects numerous intracellular metabolic processes, which are reflected by changes in the concentration of some plasma constituents. Particularly, the disease may indirectly undermine some functions of the nervous system including learning and memory through altering oxidative stress status. On the other hand, probiotics can enhance the antioxidant capacity. This study was designed to evaluate the effects of probiotics on spatial memory, maze learning and indices of oxidative stress in diabetic rats.
Methods: In this experimental study, 40 male Wistar rats were randomly allocated to 4 groups (n=10 for each): Control (CO), Control probiotic (CP), Control diabetic (DC), and Diabetic probiotic (DP). The probiotic supplement, including Lactobacillus acidophilus, Lactobacillus fermentum, Bifidobacterium lactis (334 mg of each with a CFU of ~1010), was administered through drinking water every 12 hours for 8 weeks. Using morris water maze (MWM), spatial learning and memory were evaluated. Serum insulin and oxidative stress indices, including superoxide dismutase (SOD) and 8-hydroxy-2'-deoxyguanosine (8-OHdG), were measured by standard laboratory kits.
Results: Oral administration of probiotics improved impairment of spatial learning (P=0.008) and consolidated memory (P=0.01) in the rats. Moreover, probiotic treatment increased serum insulin (P<0.0001) and serum superoxide dismutase activity (P=0.007) while it decreased their blood glucose (P=0.006) and 8-OHdG (P<0.0001).
Conclusion: Probiotic supplementation reversed the serum concentrations of insulin and glucose along with an increase in antioxidant capacity in diabetic rats. It also improved spatial learning and memory in the animals. Relevancy of the metabolic changes and behavioral functions need to be further studied.

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Background: Extremely low frequency (0-300 Hz) fields from power lines, electronic equipment and medical devices, have been reported to produce various biological effects. Global system for mobile (GSM) is most largely used in everybody's life. This system utilizes a low frequency band as well as a high frequency range of electromagnetic field. This study investigated the effects of 217 Hz electromagnetic field (the modulating signal in GSM) on spatial learning and memory in rat.
Methods: Twenty four male Wistar rat (200- 250 g) were randomly divided in to three groups as: test, sham and control. Using a Helmholtz coil system, the test group was exposed to a uniform pulsed EMF of 200 µT (micro Tesla) intensity for 4 h/day for 21 days (2 time in a day). This procedure was repeated for the sham group but with no field. All groups were trained prior to the day 21 on the 15th day for five days four trial per day in Morris Water-Maze system. Then the probe test was carried out for 60 seconds with no platform.
Results: The ANOVA test revealed that no significant differences were found between control and exposed rats in all day of learning acquisition. Also, in probe test for investigating the memory, no significant differences observed. (P≤0.05 is accepted for significant level.
Conclusion: This finding is in consistent with previous studies and indicates low frequency band of electromagnetic fields (EMF) (200 µT intensity) in cell phone may not have any effect on the learning acquisition and spatial memory in rat.