[ effect of noise pollution exposure during pregnancy on long term potentiation induction in pyramidal neurons of hippocampus CA1 area in male rat offsprings]

It is believed that cognitive processing is easily disturbed by incompatible environmental stimulations. Many studies have shown that prenatal stress affects fetal brain development. The aim of this study was to evaluate the effect of noise pollution exposure during conception period on neural activity of hippocampus CA1 area in male rat offspring. Four groups of rats including a control group with natural pregnancy and without any stress and three groups of pregnant rats exposed to daily noise stress [intensity >95 dB, between 8 A.M - 2 P.M] with durations of 1, 2 and 4 hour [s] in the last week of pregnancy were included in the study. Then, in male offsprings of these groups, fEPSP resulted from Schaffer collateral neurons of CA1 were recorded and evaluated in baseline state and after LTP induction with tetanic stimulation. Our results showed that prenatal exposure to traffic noise pollution at 3[rd] gestational week, reduces amplitude [P<0.0001] and slope of baseline synaptic activity in hippocampus CA1 area [P<0.0001] and furthermore interferes in hippocampal LTP in comparison with control group. The serum level of corticostrone in the two stressed groups [2 and 4 hours] of rats in comparison to the control showed significant increase. But, prenatal exposure to 1- hour noise pollution caused no significant difference in serum corticostrone level. Based on the obtained results, daily exposure to noise pollution in the third trimester of pregnancy for 1, 2 and 4 hour [s], attenuates fEPSP features of hippocampus CA1 area pyramidal neurons of offsprings

[Vitamin d alterations in food regimens and synaptic transmission in neuronal circuit]

In nervous system, through specific channels and some ionotropic receptors, calcium ion involves in synaptic transmission vitamin D takes an important role in cellular regulation as well. Calcium ion plays an important role in synaptic transmission through specific channels and some receptors such as NMDA receptors in the nervous system. In the present study we asked if alterations in vitamin D content of food regimens influence electrophysiological phenomena in hippocampal neuronal circuits. Adult rats under normal food regimen [CON], vitamin-D-free regimen [CON-D] or with a supplement of calcitriol [CON+D] were used in this study. Stimulating Schaffer colateral excitatory post synaptic field potentials [EPSP] were recorded in CA1 area of hippocampus. For inducing of long term potentiation [LTP] high frequency stimulation [HFS] was used as a tetanic stimulation. Changes in the amplitude of EPSPs were considered for comparison of the 3 tested groups. Our findings indicated that there was no difference between EPSP amplitude of the CON, CON+D and CON-D rats. On the other hand, LTP was induced only in the CON and CON+D animals. According to the findings, it seems that vitamin D deficiency considerably affect potentiation of the synaptic transmission. The probable mechanism can be vitamin D regulation of intracellular calcium concentration

[Effect of vitamin D deficiency and calcitriol supplementation on adult rats' learning and memory in Morris water maze]

Background: Vitamin D receptors have been presented in the areas involved in learning and memory. This study was done to assess the effect of the vitamin D deficiency and calcitriol supplementation on spatial learning and memory

Materials and Methods: Twenty seven male rats were divided into three groups [n=9 for each]: receiving normal [Control], diminished vitamin D [C-D] and calcitriol supplement [C+D] regimens for 45 days. The animals were introduced to the Morris water maze [MWM] trials [4trials/day for 5 consecutive days]. The delay in finding and distance passed to reach the target platform were measured as spatial learning. The probe test was performed on the 5[th] day of experiment

Results: The C-D group needed a longer time to reach the platform than the control and C+D animals [P<0.0001], demonstrating that vitamin D deficiency negatively affected the maze learning. On the other hand, calcitriol supplementation did not significantly influence the spatial learning. The probe trial was not affected by either vitamin D deficiency or calcitriol supplementation

Conclusion: Although vitamin D deficiency deteriorates the maze learning it dose not affect the spatial memory consolidation. Also, calcitriol supplementation for 45 days is not effective in cognitive phenomena

[Role of melatonin receptors in spatial learning of rats exposed to continuous light]

During critical period of mammal's CNS development, interaction of genetic and experience driven processes affects almost their all behaviors in adolescence. The aim of this study was to assess interaction of melatonin and its antagonist, Luzindole on the spatial learning and memory of the rats [Morris Water Maze [MWM]] exposed to continuous light. This experimental study included sixty 45-day-old male rats which were randomly allocated in two groups; control group went through cycles of 12 hours in light/12 hours in dark from birth to the end of the study and the light exposed group was reared in light. Each group also, had 3 subgroups: control, receiving melatonin and receiving luzindole [n=10 for every group]. Using MWM, the animals learning and memory was tested for 5 days. Our results indicated that in the learning phase, the light exposed animals spent more time to find the hidden platform than the control group. Luzindole improved the learning ability in light exposed animals. Melatonin also, slackens the spatial learning of the control animals. luzindole improved spatial learning of the light exposed rats. Light exposure and melatonin had no effect on the memory of these animals. Luzindole only caused a disturbance in spatial memory of the rats in the control group. Light exposure and melatonin impair rat's spatial learning. Non of these two interventions influenced spatial learning of the rats

[Light deprivation-related defect in spatial navigation of water maze]

Sensory signals and intrinsic activity of the neuronal circuits deeply influence on developing the sensory systems in early life. Light deprivation of animals is known as an established method in assessment of environmental signals in development of the nervous system. In this experimental study eighteen male rats at 75 days of postnatal age were used. The animals were divided in two groups, one reared in a cycle of 12light/12dark [light reared-LR] and the other keep in darkness since birth through experiment [Light deprived- LD]. The animals were trained in a Morris water maze for spatial memory. They must navigate the maze until finding a platform hidden 1 cm below of water. Then, the time required and the distance spent to find the platform were measured for assessment of the animal behavior. Each animal was given 4 trials/day and the experiment lasted for 6 days. This stage was followed by probe and postprobe tests to evaluate how the learning is consolidated. The results indicated that, compared to their LD counterparts, the LR group was superior in finding the platform where they required a noticeable shorter time to hit the platform [p<0.009]. Also, animals in the LR group steered a shorter distance to find the target than did the LD animals [p<0.034]. While the two groups elicited a considerable difference during the first half of the experiment both LR and LD rats demonstrated a similar behavior over the second half of the study. The light deprivation negatively influences the spatial navigation in water maze so that the visually deprived rats show less ability in searching the maze based on the spatial cues

Correlation of insulin resistance and impaired glucose metabolism in Tehranian adults: Tehran lipid and glucose study

Insulin resistance and undersecretion play major roles in the pathogenisis mechanism of diabetes mellitus. This study evaluates the correlation between insulin resistance [by HOMA-IR] and the prediction of impaired carbohydrates metabolism. Individuals with from among participants of the Tehran Lipid Glucose Study normal FBS and GTT [TLGS] were followed for 3 years. Of these, 3 years later, some cases developed DM type 2, IGT, IFG and IFG-IGT cases remained normal. Insulin and fasting plasma glucose levels were measured and HOMA-IR index was calculated. Body mass index [BMI], waist circumference, waist to hip ratio [WHR], systolic and diastolic blood pressure, glucose tolerance test, serum lipid profile, history of smoking and family history of diabetes at the beginning and after 3 years were determined. For comparison of variables chi-square test and ANOVA were used. Prediction of development of diabetes, IGT, IFG, IFG-IGT according to quarters of HOMA-IR before and after modifying of confounders were estimated by logistic regression analysis. Power of prediction of multiple modeling was evaluated by the Roc curve. Of the 255 normal cases from among TLGS participants followed for 3 years, when 30 cases developed DM type 2, 89 individuals IGT, 57 IFG and there were 26 cases of IFG-IGT with 53 cases remaining normal. In the first stage there was no difference between study groups in sex, total cholesterol, HDL cholesterol, LDL cholestrol, family history of DM, cigarette smoking and physical activity. Mean fasting blood glucose was higher in cases who developed IGT, DM, IFG, IFG-IGT than in normal cases [91.2 +/- 7.9 mg/dL, 96.2 +/- 9.0 mg/dL, 98.1 +/- 8.8 mg/dL and 98.9 +/- 8.5 mg/dL vs 86.8 +/- 9.9 mg/dL in the normal group respectively, p = 0.02, p < 0.001]. Mean HOMA-IR in cases who developed DM, IFG, IFG-IGT was significantly higher than in normal cases [1.9 +/- 1.0, 2.2 +/- 1.3, 2.5 +/- 1.6 respectively vs 1.0 +/- 0.9 in normal cases p = 0.014, p < 0.001, p

Dose dependent effect of memantine on long term potentiation in the CA 1 area of the hippocampus

Generally, NMDA receptor antagonists inhibit learning and long-term potentiation [LTP]. However, it has been suggested that direct tonic activation of NMDA receptors, in contrast to learning, may lead to an increase in synaptic "noise". Uncompetitive NMDA receptor antagonist memantine can paradoxically reverse deficits in learning and synaptic plasticity, and restore LTP impaired by tonic NMDA receptor activation. Adult rats weighed 200 to 250g were used in this in vivo study. Stimulating Schaffer collaterals field excitatory postsynaptic potentials [fEPSPs] were evoked in neurons of the CA1 area of the hippocampus. For induction of LTP, high frequency stimulation was applied to the path. Pre- and post-tetanic fEPSPs were recorded extracellularly in the anesthetized rats. Test groups were administered intraperitoneally with memantine [10 mg/kg or20 mg/kg] and the control animals received equal volumes of saline. Our results express that the drug has no effect on the baseline EPSPs. The tetanic stimulation induced a pronounced LTP in the control group lasting at least 2 hours. The animals treated with 10mg/kg of memantine also displayed a significant LTP; however, the potentiation was lower than the controls. The high frequency stimulation under administration of 20mg/kg of memantine failed to induce LTP in the fEPSPs. These findings point out a dose dependent attenuation of LTP by memantine. Comparison of the present data and those indicating the ability of memantine to restore LTP led us to conclude that, due to the activation level of the recording path, this moderate affinity NMDA receptor antagonist displays different effects on potentiation of hippocampal recordings

Effect of light deprivation and sex on the strategy selection of rats in radial maze

During the early postnatal age environmental signals underlie development of sensory systems. The visual system is considered as an appropriate system for evaluation of the role of sensory experience in postnatal development of sensory systems Light [LR-control] and dark reared [DR] 40 days old rats were used for adjacent arms tasks. The animals were subjected to two trials each day on a radial arm maze. The experiments were performed in 3 stages. In the first stage, the rats had to search the maze with while all arms were baited. During the second and third stages, only 4 adjacent arms were baited, however, in the third stage the place of the adjacent arms was changed between the daily trials. The findings were considered for 1- the number of correct entries and 2- selection of the adjacent arms. Our results indicated that both the LR and DR animals equally entered correct arms. In the adjacent arms task, however, the control group significantly outperformed the DR animals. Concerning sex dependency of the tasks while, at least partly, the LR males and females differently searched the maze the DR group represented no sex differences in their performances These findings suggest that the lack of visual experience is likely to influence the strategy selection and sex differences as well. Also the difference between performances of the LR and DR animals is probably due to the males rather than females behavior