Hippocampus ; Learning ; Maze Learning ; Memory ; Microwaves/adverse effects*

The objective of this study was to elucidate the effect of chronic stress (CS) on dopamine (DA) level and synaptic efficiency in the hippocampal dentate gyrus (DG) during spatial learning and memory. Sprague Dawley (SD) male rats were randomly divided into control group and CS group (n = 10). CS group was treated with chronic mild unpredictable stress, and control group did not receive any treatments. The levels of epinephrine and corticosterone (CORT) in serum were measured by using enzyme-linked immunosorbent assay (ELISA); the spatial learning and memory abilities of rats were measured by Morris water maze (MWM) test. Meanwhile, the amplitude of field excitatory postsynaptic potential (fEPSP) and concentration of DA in the DG region were determined by in vivo electrophysiology, microdialysis and HPLC techniques during MWM test in rats. After that, the DA D1 receptor (D1R) and its key downstream members in DG were examined by immunohistochemistry or Western blot assay. The results showed that the levels of epinephrine and CORT in the serum of the rats in CS group were significantly increased compared with those in the control group (P < 0.05). In CS group rats, the escape latency was significantly prolonged and the number of platform crossing was markedly decreased during MWM test, compared with those in control group (P < 0.05). Furthermore, the amplitude of fEPSP in the DG was not changed during MWM test in CS rats, while it was significantly increased on the 3rd day of MWM test in control group (P < 0.05). Compared with baseline or control group, CS group showed significantly increased DA level from the 1st to 3rd days of MWM test in the DG (P < 0.05). In addition, the protein expression of D1R was markedly up-regulated in the DG in CS group, while the protein expression levels of p-PKA, p-CREB and BDNF were significantly reduced, compared with those in control group. These results suggest that CS may impair spatial learning and memory abilities in rats through the enhancement of the DA levels in the hippocampal DG.
Animals ; Dentate Gyrus ; Dopamine ; Hippocampus ; Male ; Maze Learning ; Rats ; Rats, Sprague-Dawley ; Spatial Learning ; Spatial Memory

OBJECTIVE: To investigate the effects of aminooxyacetic acid (AOAA) on learning and memory ability and possible mechanisms in rats with chronic alcoholism. METHODS: Sixty SD male rats were randomly divided into three groups on average.The model group rats and the remedy group rats were fed with the water containing (v/v) 6% alcohol for 28 days.After 14 days, the remedy group rats were treated with AOAA (5 mg/kg·d) by intraperitoneal injection once a day for 14 days and the other two group rats were treated with the equal amount of saline by intraperitoneal injection every day.Five days before the end of the experiment, the water maze test was carried out to test the learning and memory ability of rats for 5 days.Subsequently, the content of HS, the activity of ATP enzyme and the expression of 5-HT in hippocampus were measured. RESULTS: Compared with the rats in the control group, the latency and the swimming distance of the 2nd to the 4th day, the content of HS in hippocampus of rats in the model group were all increased, the mitochondrial ATP enzyme activity in hippocampus and the positive expression of 5-HT in hippocampus CA1 and CA3 of rats in the model group were decreased (<0.01).Compared with the rats in the model group, the latency and the swimming distance of the 2nd to the 4th day, the content of HS in hippocampus of the rats in the remedy group were decreased, the mitochondrial ATP enzyme activity in hippocampus and the positive expression of 5-HT in hippocampus CA1 and CA3 of rats in the model group were increased (<0.01). CONCLUSIONS AOAA could alleviate the symptoms of chronic alcoholism rats, which may be related to the effects of AOAA on the content of HS, the mitochondrial enzyme activity and the expression of 5-HT in hippocampus.
Alcoholism ; Aminooxyacetic Acid ; Animals ; Hippocampus ; Learning ; Male ; Maze Learning ; Memory ; Rats ; Rats, Sprague-Dawley

Animals ; Female ; Hippocampus ; Learning ; Male ; Maze Learning ; Neurons ; Pregnancy ; Proteomics ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the effects of chronic stress on spatial cognitive ability in different sex mice.

METHODSThirty-two adult KM mice were divided into four groups (n=8): male control and chronic stress group, female control and chronic stress group. We used the modified Kaz's methods to build on the chronic stress model of mice, and then used the place navigational testing and the probe trial testing by the Morris water maze to measure the spatial cognitive ability of mice.

RESULTSFollowing two weeks stress treatment, in the place navigational testing, to male group, the average latency to find the platform in water maze of chronic stress group was longer than that of the control; to female group, the average latency of chronic stress group was shorter than the control. Moreover, the male stress group showed faster swimming speed but longer latency to find the platform. In the probe trial testing the female chronic stress group spent more time in the target quadrant compared to the male chronic stress group.

CONCLUSIONTwo weeks' chronic stress could impair male mice's spatial cognitive ability, but improve the female's.

Animals ; Brain ; physiology ; Cognition ; physiology ; Female ; Male ; Maze Learning ; Mice ; Sex Factors ; Stress, Physiological ; physiology

In order to investigate if the experiment-time affects cognitive performance in aged rats in different learning and memory behavioral tests, the aged Sprague-Dawley (SD) rats were divided into two groups randomly and subjected to open field test, Morris water maze test and social discrimination test. The experiment of one group was conducted in 8:00 - 11:00 AM (AM group), and the other group in 15:00 - 18:00 PM (PM group). PM group exhibited higher locomotor activity than AM group in the open field test. Compared with AM group rats, PM group rats had significantly shorter swimming distance and escape latency to find the platform in Morris water maze training session, but no significant difference in the swimming velocity was observed between the two groups. And in probe-test, PM group spent more time in target quadrant than AM group. These results revealed that PM group showed better spatial learning and memory abilities than AM group. However, there was no significant difference between the two groups in social investigation index in social discrimination test. These results show that experiment-time may affect cognitive performance in Morris water maze but not in social discrimination task in aged rats. And the results indicate that experiment-time affects cognitive performance of aged rats selectively in different learning and memory behavioral tasks.
Aging ; Animals ; Behavior, Animal ; Cognition ; Maze Learning ; Memory ; Rats ; Rats, Sprague-Dawley ; Swimming ; Time Factors

OBJECTIVETo examine the effect of docosahexaenoic acid (DHA) deficiency in brain on spatial learning and memory in rats.

METHODSSprague Dawley rats were fed with an n-3 fatty acid deficient diet for two generations to induce DHA depletion in brain. DHA in seven brain regions was analyzed using the gas-liquid chromatography. Morris water maze (MWM) was employed as an assessing index of spatial learning and memory in the n-3 fatty acid deficient adult rats of second generation.

RESULTSFeeding an n-3 deficient diet for two generations depleted DHA differently by 39%-63% in the seven brain regions including cerebellum, medulla, hypothalamus, striatum, hippocampus, cortex and midbrain. The MWM test showed that the n-3 deficient rats took a longer time and swam a longer distance to find the escape platform than the n-3 Adq group.

CONCLUSIONThe spatial learning and memory in adult rats are partially impaired by brain DHA depletion.

Animals ; Brain ; metabolism ; Docosahexaenoic Acids ; metabolism ; Maze Learning ; physiology ; Memory ; physiology ; Rats ; Rats, Sprague-Dawley

Air Pollution, Indoor ; adverse effects ; Animals ; Male ; Maze Learning ; Memory ; Mice ; Mice, Inbred Strains

BACKGROUNDAs the widespread use of electric devices in modern life, human are exposed to extremely low frequency magnetic fields (ELF MF) much more frequently than ever. Over the past decades, a substantial number of epidemiological and experimental studies have demonstrated that ELF MF (50 Hz) exposure is associated with increased risk of various health effects. The present study examined the effects of chronic exposure to ELF MF on anxiety level and spatial memory of adult rats.

METHODSThe 50-Hz ELF MF was used during the whole experimental procedures and the value of magnetic field (MF) was set to 2 mT. Adult rats were divided randomly to control, MF 1 hour and MF 4 hours group. Anxiety-related behaviors were examined in the open field test and the elevated plus maze; changes in spatial learning and memory were determined in Morris water maze after 4 weeks of daily exposure.

RESULTSRats in MF 4 hours group had increased anxiety-like behaviors with unaltered locomotor activity. In the Morris water maze test, rats had reduced latency to find the hidden platform and improved long-term memory of former location of platform without changes in short-term memory and locomotor activity.

CONCLUSIONChronic ELF MF exposure has anxiogenic effect on rats, and the promoting effects on spatial learning and long-term retention of spatial memory.

Animals ; Anxiety ; physiopathology ; Electromagnetic Fields ; Male ; Maze Learning ; physiology ; Memory ; physiology ; Rats ; Rats, Sprague-Dawley

Animals ; Environment ; Female ; Male ; Maze Learning ; physiology ; Memory ; physiology ; Microarray Analysis ; Rats ; Rats, Sprague-Dawley ; Weaning