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Sound pollution is known as an annoying phenomenon in modern life. Especially, development of organisms during fetal life is more sensitive to environmental tensions. To address a link between the behavioral and electrophysiological aspects of brain function with action of hypothalamus-pituitary-adrenal (HPA) axis in stressed animals, this study was carried out on the male Wistar rats prenatally exposed to sound stress. Groups of pregnant rats were exposed to noise stress for 1, 2, and 4 hour(s). The degree of anxiety and the spatial memory were evaluated by elevated plus maze and Morris water maze, respectively. Basic synaptic activity and long-term potentiation (LTP) induction were assessed in the CA3-CA1 pathway of hippocampus. The serum level of corticosterone was measured in the pregnant mothers and the offspring. The behavioral experiments appeared that the stressed animals performed considerably weaker than the control rats. The prenatal stress negatively affected the basic synaptic responses and led to a lower level of LTP. The pregnant animals showed an increased serum corticosterone in comparison with the nonpregnant females. Also the offspring exposed to the noise stress had a more elevated level of corticosterone than the control rats. Our findings indicate that the corticosterone concentration changes markedly coincides the results of behavioral and electrophysiological experiments. We conclude that, similar to other environmental stresses, the sound stress during fetal life efficiently disturbs both cognitive abilities and synaptic activities. The changes in action of HPA axis may contribute to problems of the brain function in the prenatally stress exposed animals.

Objective Alzheimer's disease (AD) is one of the most important neurodegenerative disorders. It is characterized by dementia including defi cits in learning and memory. The present study aimed to evaluate the effects of aqueous extract of lavender (Lavandula angustifolia) on spatial performance of AD rats. Methods Male Wistar rats were fi rst divided into control and AD groups. Rat model of AD was established by intracerebroventricular injection of 10 g A1-42 20 d prior to administration of the lavender extract. Rats in both groups were then introduced to 2 stages of task learning (with an interval of 20 d) in Morris water maze, each followed by one probe test. After the fi rst stage of spatial learning, control and AD animals received different doses (50, 100 and 200 mg/kg) of the lavender extract. Results In the fi rst stage of experiment, the latency to locate the hidden platform in AD group was signifi cantly higher than that in control group. However, in the second stage of experiment, control and AD rats that received distilled water (vehicle) showed similar performance, indicating that the maze navigation itself could improve the spatial learning of AD animals. Besides, in the second stage of experiment, control and AD rats that received lavender extract administration at different doses (50, 100, and 200 mg/ kg) spent less time locating the platform (except for the AD rats with 50 mg/kg extract treatment), as compared with their counterparts with vehicle treatment, respectively. In addition, lavender extract signifi cantly improved the performance of control and AD rats in the probe test, only at the dose of 200 mg/kg, as compared with their counterparts with vehicle treatment. Conclusion The lavender extract can effectively reverse spatial learning defi cits in AD rats.

The present findings signify the crucial role of vitamin D on the basic synaptic transmission and synaptic plasticity.

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