Vitamin D deficiency impairs spatial learning in adult rats

Background: through its membrane and intracellular receptors, vitamin D regulates many vital functions in the body including its well-known actions on musculoskeletal system. Growing body of evidences demonstrate that vitamin D undergoes some of behavioral aspects of neurocognition. The present study was designed to evaluate the effect of food regimens without vitamin D or with a supplement of 1,25[OH]2D3 on spatial performance of adult rats

Methods: the animals were trained in the Morris water maze to find a hidden platform. The time spent and the distance traveled to find the platform, speed of navigation and the percentage of unsuccessful trials were considered for assessment of the task learning

Results: our findings indicated that the vitamin D-deprived rats had a significant lower performance compared to both the controls and the animals receiving 1,25[OH]2D3 supplementation. Concerning the unsuccessful trials, lack of vitamin D resulted in the highest failures in the maze navigation. The regimen with additional 1, 25[OH] 2D3 did not considerably influence learning of the maze task

Conclusion: we concluded that while vitamin D deficiency deteriorates the spatial task learning, the 1,25 [OH] 2D3 supplementation did not effectively underlie the maze performance. Iran. Biomed. J. 17 [1]: 42-48, 2013

[ effect of co-administration of lactobacillus probiotics and bifidobacterium on spatial memory and learning in diabetic rats]

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. 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 tilde10[10]], 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. 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]. 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.

[Attenuating effects of aqueous extract of Lavandula angustifolia on alzheimeric rat's spatial learning]

Alzheimer is a progressive demential disease with destruction of brain neurons and severe deficiency of memory. For many years, plenty efforts was devoted to find an appropriate and efficient way for treatment of the disease. The present study was designed to assess if the herbal medicine Lavandula Angustifolia shares the Morris water maze training in improvement of learning behavior of the Alzheimeric rats. This experimental study was carried out on 40 wistar male rats randomly divided in 4 groups: Two control groups [CO and ALZ] received 1 ml normal saline, and the other 2 groups [CO+E and ALZ+E] received 1000 mg/kg body weight Lavender extract, intra-peritoenally. To assess spatial learning of the animals, they were introduced to the Morris water maze to locate a fixed hidden platform. Probe test was applied to evaluate the memory consolidation. The time elapsed and distances passed in the correct quadrant were analyzed by ANCOVA test. The CO group spent less time and distance to find the hidden platform than ALZ group. Also, CO+E and ALZ+E compared to CO and ALZ expended more time and distance to find platform. There was no difference between groups in probe trial test. The behavioral training positively influenced the maze learning in the Alzheimeric subjects. Lavender extract with dose of 1000 mg/kg is effective on improvement of the Alzheimer's disease

Dark and light rearing during early postnatal life impairs spatial learning of rats in Morris water maze

In early postnatal life, sensory-driven processes deeply affect structure and function of sensory cortices. Because some visual signals pass from visual cortex to the hippocampal formation, the aim of this study was to investigate the effects of change in visual experience on rat's spatial learning and memory. This experimental study was carried out on 30 Wistar male rats [45 days old] which were randomly distributed into 3 groups; the CO [Control group] was in 12 light/12 dark cycle through birth to the end of the study, the LR [Light Reared] group was in complete lightness and the DR [Dark Reared] group was in complete darkness [n=10 for each]. Using MWM [Morris Water Maze], the animals learned to find a hidden platform for 4 trials per day during 5 days. After removing the platform, spatial memory was tested at day 5 in one trial [probe trial]. Our results indicated that in the learning stage, the CO rats spent less time and distance to find the hidden platform than the other groups. There was no difference between all groups in probe trial. Change in visual experience impairs spatial learning of rats in Morris water maze and their spatial memory formation is not influenced

histological evidences for developmental alternations in the transmitting time of impulses along the thalamocortical tract

Change in transmitting time of impulses along axons is traditionally attributed to two parameters: the myelin formation and the diameter of neurite, both rising during the postnatal development. In the previous study, we showed that conduction velocity of the fibers projecting from the thalamus to the layer IV of the somatosensory [barrel] cortex increases as a function of age. However, the conduction velocity change is not parallel outside and inside of the barrel cortex. Here, we tried to find a probable relationship between disparity of the conduction velocities and the extent of myelination of the thalamocortical pathway. Our results indicate that myelin is evident on the extra-cortical but not intra-cortical fibers at ages >10 days. At the older age, however, myelin wholly covers the fibers both outside and inside of the cortex, more considerably in the former. Our results demonstrate that difference in the conduction velocities of the extra-cortical and intra-cortical axons, at least to more extent, can be attributed to myelination dissimilarity along the thalamocortical fibers

Prenatal alcohol exposure and dysfunction of hippocampal formation in cognition

Background: Fetal alcohol syndrome is associated with numerous problems in the development and function of the brain. Learning and memory deficits are among well known effects of prenatal exposure to alcohol

Objective: This study aimed to examine the spatial working memory of 60-day old rats who were exposed to alcohol during their fetal life and to find the relation between the possible alcohol-impaired spatial memory and gestational period of exposure to alcohol

Materials and Methods: Pregnant rats in different stages of gestation period were administered with ethanol. Using a radial arm maze, the offspring were subjected to spatial working memory training at 60 days of postnatal age

Results: The rats exposed to ethanol during the first 10 days of fetal life indicated lower performances compared to the controls. Those receiving alcohol during the second half of pregnancy period had no problem in maze navigation. Behavior of the animals exposed to alcohol during the first and the second quarter of the gestation period demonstrated that only the latter were weak in solving maze tasks. The groups related to the third and the forth quarter of gestation period had a similar behavior with the control group. Comparison of the animals' performances in all groups revealed that only the second quarter group was the most disadvantaged

Conclusion: Our data indicates that the second quarter of the gestation period is more sensitive to harmful effects of alcohol on the areas of brain involved in learning and memory. Since the hippocampus is central in cognitive functions and this part of brain is highly vulnerable to alcohol effects it can be concluded that the hippocampus is mostly affected in the second quarter of prenatal life

Postnatal changes of conduction velocity of the fibers in and out of the mouse barrel cortex

There are some conflicts about constancy of conduction velocity [CV] in a given tract of nervous system. By recording excitatory postsynaptic currents [EPSC] in layer IV of the somatosensory cortex we tried to clear changes in CV of thalamocortical tract of mice aged 3 to 50 days old. Field potentials and EPSC were recorded in the layer IV by stimulation of ventrobasal nucleus of thalamus [VB] and white matter [WM]. Our results indicate that in mice aged 3 through 17 days old, CV of EPSC evoked by WM and VB stimulation increased up to 2 and 15 times, respectively. Also, the data from field potentials match those from EPSC. CV enhancement of the fibers out of cortex may contribute to myelination as well as increased diameter of neurites. However, it is not the case for WM matter stimulation-evoked responses