Abstract: Method microinjection aging model and hippocampus β AP, detected opening behavior of rats, Y- maze discrimination learning and passive avoidance-time response to changes in the studied beta] with D- galactose (D-gal) - The effect of amyloid ( β AP) on the opening behavior and learning and memory ability of aging rats . The results showed that the spontaneous activity and the investigation behavior of rats in D-gal + NS group and D-gal + β A P group were different in the new environment. , learning and memory impairment, with NS + NS group there was a significant difference (P <0. 05, P < 0. 01). the paper concluded that β AP was used in combination with D-gal can lead to cerebral aging degree of aggravation The ability to learn and remember is significantly weakened .
Key words : β - amyloid ; opening behavior ; learning and memory ; aging
β - amyloid (β - amyloidp rotein, β AP ) is the brains of patients with Alzheimer unique to a protein, its role in the pathogenesis of senile dementia has attracted attention biochemical studies indicate, β. - amyloid senile dementia, cerebral cortex and the hippocampus in patients with senile plaques (SP) of the main component, which is formed close to the process of AD pathology has been reported on the toxicity of β a P normal rat hippocampal neurons, but relevant β. AP action on aging rats, both home and abroad has not been reported, the present experiment attempted hippocampal injections beta] AP on the basis of D- galactose induced aging animal model, to observe the opening behavior and spatial learning and memory in rats resolution Maintain the impact of ability .
1 Materials and methods
1.1 Animals and reagents
Male SD rats weighing 100 ~ 120g (Jiangsu Province Experimental Animal Center), β A P, Sigma (β A P1 -40, Lot NO . 76 H49611), D- galactose (D-gal) as Shanghai Reagent second plant products .
1.2 Grouping and model building
Rats were randomly divided into 4 groups : 1 saline N S + N S group ; 2 N S + β A P group ; 3 D-gal + N S group ; 4 D-gal + β A P group - 1 continuous injection for 6 weeks to establish aging animal model ; ①, ② group ③, ④ animals by intraperitoneal injection D- galactose:.. 50 mg · kg- 1d animals injected intraperitoneally with saline for the bilateral hippocampal injections β A P, 1 μ L injection on each side in the 4th week . (. 40 mg kg-1 ):; (4 μ g / μ L) in the control group injected with saline injected hippocampus positioning method intraperitoneal injection of 4% sodium pentobarbital anesthesia stereotaxic apparatus (Japan NARISHIGESN - Type 3 ) fixed on the coordinates, according to the map , previous chimney positioning : A P = - 3 . 5 mm , ML = ± 2 . 0mm , H = 2 . 7 mm , drill the skull , use the micro-injector to vertically insert the needle , each side injection time 5min, needle 5min, slowly from the needle, suture the skin after local disinfection, intramuscular injection of antibiotic anti-infectives.
1.3 Behavioral testing
Continuous intraperitoneal injection for 6 weeks .
. 131 open field (open field): The animals were placed in the center of the circular bottom opening detecting cells, cell number recorded min in 3 min running (Locomotion) therethrough, hind limb standing (Rearing) frequency comb The number of (grooming) and the number of fecal particles . The differences between self-issued and explored behaviors of rats in different groups were compared .
1 . 3 . 2 　 Y - maze discrimination learning (Y- maze discrimination learning) ability to detect the Y- maze trisection radiation reflector box to electrical shock in rats.
After fled safety zone once the correct response, the test 10 times 9 times (90%) of correct responses, the standard set for learning recording each rat to reach the learning criteria training frequency detection process by the computer to complete all.
1 . 3 . 3 one-time passive avoidance response (o ne- t rial passive avoidance respo nse) according to the darkening habit of the rat , record its residence time on the channel , that is , step-t hrough latency ( STL ) ; animals given immediately after entering the dark box shock (0 3 mA, 5 s. ); detecting S TL rats 24 h after S TL as an index to memory retention, S TL indicates hold, the better the longer the memory of the shock detection. 240 s in the present experimental data is limited (X ± SŠX (X represents differences between groups using the t test; disposable passive avoidance response test using non-parametric Mann- whit ney
2 results
2.1 the opening behavior of the different groups of rats were observed (Table 1), showed statistical processing, various parameters in the open field, D-gal + β AP animals with NS + NS group fecal particle count significantly different (P < 0.05), while the number of cells is extremely run significantly reduced (P <0. 01), the former locomotor activity and decreased in the reaction to explore novel environments, intense fear state is also reduced. D-gal + NS group were run moving the number of cells with NS + NS group have significant difference (P <0. 05). NS although no significant difference between NS group and the NS + β A P set +, but the running number of cells, the standing times were decline, indicating that β a P alone has some influence on locomotor activity and exploratory behavior in rats in a novel environment.
twenty two 　 Y- maze discrimination learning ability detection
The number of trainings required to achieve the standard of learning , N S + N S group : 21.4 ± 2. 6 ; N S + β AP group : 34.6 ± 5 . 5 ; D-gal + NS group : 42.4 ± 5. 4 D-gal + β A P group : 48 . 0 ± 5 . 6 . There was no significant difference between the first two groups ( P > 0.05 ). There was a significant difference between the D-gal + NS group and the NS + N S group ( P < 0.05], and the D-gal + β PA group compared with the N S + N S group , the number of training required to reach the standard of learning was significantly increased (P < 0.01), indicating that D-gal- induced aging model rats The ability to distinguish learning is significantly reduced , and the injection of β AP in the aging animal model in Shanghai has significantly reduced learning ability .
2 . 3 one-time passive avoidance reaction
D-gal + β AP group memory retention decreased, 24 hSTL significantly reduced after the shock, with NS + NS group, and D-gal + NS group there was a significant difference (P <0. 05). Comparison between other groups , the difference is not significant , but the memory retention ability is gradually decreasing
Low trend
3 Discussion
Studies have reported that rats continuous injection of D- galactose induced mimetic aging effects, can lead to decreased learning and memory abilities of animals, the brain
Increased levels of superoxide anion radicals, superoxide dismutase (SOD) activity decreased, MDA and lipofuscin increased. That said,
Ming D- galactose-induced accumulation of free radical induced lipid peroxidation damage, is intended to cause a change of aging, which will inevitably cause senescence decline in brain function. Β AP are typical senile dementia earliest pathological characteristics. Some researchers believe, β AP can cause learning and memory impairment, cognitive impairment and other factors originating AD various pathologies and clinical manifestations. β AP neurotoxicity and deposition have higher concentrations of β AP can causing neurodegeneration and death; neurotoxicity of β AP role may enhance or increase the damaging effects of various noxious stimuli cells, in addition it has a direct cytotoxic but Morimoto reported in rat hippocampal neurons, injected alone. β AP can not generate specific neurotoxic effects can only cause a small amount of neuronal degeneration. both in cells in vitro or in vivo studies, β AP whether neurotoxic effects still controversial, the reason may be used by β AP The concentration is different.
The results of this study
It shows the hippocampus β AP injected alone can not cause a significant change in behavior, but in animal models of aging on the basis of β AP after treatment, can lead to locomotor activity and learning and memory animal behavior decreased significantly, indicating D- galactose and β AP has superimposed effects of learning and memory is an advanced brain function, learning and memory impairment is a manifestation of brain function decline. Therefore, the present results suggest that, in D- galactose induced aging on the basis of the animals, the hippocampus injection of β AP, as expected closer an animal model of AD, but if it has a variety of pathological features of AD, yet further study
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