Growing up in comfort: Environmental enrichment shapes maternal approach and sex differences in offspring neuroendocrine profiles in laboratory mice.

Objective To explore the impacts of enriched environment(EE), which has different initiation time points and intensity, on the neural and ethological prognosis and contents of myelin basic protein(MBP) of neonatal rats with hypoxic-ischemic brain damage (HIBD). Methods HIBD rat models were established. Rats were divided into the early, the intermediate and the late intervention groups, which experienced EE from 7, 14 and 21 days after HIBD for 14 days. The early and intermediate intervention groups were then divided into 6-h and 24-h groups, which experienced EE intervention for 6 hours or 24 hours respectively each day. Trapeze tests and water maze tests were carried out to detect the neural and ethological prognosis. Immunohistochemical method was used to detect MBP of the brain white matter, and the percentages of positive cells with MBP were detected by an image analyzer. The contents of MBP were measured. Results The trapeze test scores of the early and intermediate sham operation group, HI group, early 6-h and 24-h EE groups and the intermediate 6-h and 24-h EE groups, the late sham operation group, the late HI and late EE intervention group were (4.05±0.88) scores, (2.35±1.02) scores, (3.67±1.12) scores, (3.50±1.41) scores, (3.50±0.93) scores, (3.56±1.13) scores, (4.00±0.89) scores, (2.17±1.17) scores, (3.50±0.92) scores, respectively. The trapeze test scores of early, intermediate and late EE groups were higher than those of the HI groups in the same period. There was no significant difference between the early, the intermediate 6-h EE groups and 24-h EE groups. Scores of water maze of each corresponding group were (40.68±23.77) seconds, (56.66±10.96) seconds, (46.49±19.27) seconds, (51.72±20.46) seconds, (38.20±18.36) seconds, (47.96±20.65) seconds, (38.63±20.44) seconds, (59.66±13.81) seconds and (45.93±22.45) seconds, respectively. The water maze scores of the early, the intermediate 6-h EE group and the late 24-h EE groups were higher than those of the HI groups in the same period. There was no significant difference between the early, the intermediate 6- h EE groups and the 24-h EE groups. The relative abundance of MBP of the early and intermediate and the late HI groups were 6.32±1.63 and 6.74±2.19, and significantly less than that of the sham groups in the same periods, which were 9.09±1.69 and 9.37±2.46. The relative abundance of MBP of early 6-h and 24-h groups, the intermediate 6-h and 24-h groups and the late EE group was 7.84±2.51, 8.05±1.86, 8.89±2.29, 8.48±2.67 and 7.98±2.09, respectively, which was significantly higher than that of the HI groups in the same periods. It showed that the neural and ethological prognosis of neonatal rats with HIBD could be improved, no matter the intervention began in the early, the intermediate or the late periods, or the intervention time was 6 hours or 24 hours each day. And relative abundance of MBP in the white matter increased with EE. Conclusions EE intervention has a long window stage for young rats. EE intervention could improve the neural and ethological prognosis of rats with HIBD. EE intervention could elevate the contents of MBP in the white matter, which could be one of the mechanisms for EE to improve the neural and ethological prognosis of rats with HIBD. Key words: Cerebral hypoxia; Cerebral ischemia; Enriched environment; Myelin basic protein; Infant, newborn

Environmental Novelty Activates β2-Adrenergic Signaling to Prevent the Impairment of Hippocampal LTP by Aβ Oligomers

Objective To study the effects of enriched environment on the capacity of learning and memory and expression of brain derived neurotrophie factor(BDNF) expression of CA1 hippocampus in Wistar rats. Methods 20 male Wistar rats were raised from weaning(21 days old) to young adulthoed(50 -60 days old) in either an enriched or normal environment. The ability of learning and memory was measured with the Morris water maze test,and the expression of BDNF of CA1 hippocampus neuron was detected by immunohistochemistry. Results During Morris water maze test, the mean latency in enriched environment group was significantly shorter than that in the normal control group(24.37±5.45)s Vs (31.28±5.39)s;the time taken to cross the target in enriched environment group was significantly more than that in the normal control group(3.38±0.79)Vs (2.21± 0.49);the swimming distance of platform quadrant increased in the enriched environment group, and the decreased gray intensity of BDNF expression in CA1 hippoeampus was found in the enriched environment group. Conclusions Enriched environment can improve the capacity of learning and memory of the rats, which were realized may be through BDNF pathway. Key words: Enriched environment; Learning and memory; Brain derived neurotrophie factor(BDNF)

Objective To explore the influence of environment early in life on learning and memory abilities and neuroglobin (Ngb) expression. Methods Forty-five newborn,male,Sprague-Dawley rats were randomly divided into an EE (enriched environment) group,an EI (isolated environment) group and a normal control group,with 15 rats in each group.The EE and EI group rats lived in those environments for their first 28 days of life.The step-down test was used to measure the rats'learning and memory abilities on the 29th day.Ngb expression was examined using immunohistochemical methods. Results The step-down test showed learning and memory scores for the EE group rats of (9.67±0.49) and (9.80±0.56) respectively,significantly higher than those of the control group,(8.67±0.72) and (8.93±1.10).The learning and memory abilities of the EI group were the lowest among the three groups,with scores of only (7.07±1.98) and (7.67±0.98 ),respectively.The latency of the first electric shock was (166.33±36.08)s in the EE group and significantly shorter than that in the control group (108.93±73.26) s.The EI group showed the longest average latency (44.93±45.03)s.Average Ngb expression as reflected by the integrated optical density in the EE group was (224.56±89.09) in the frontal cortex and (127.70 ± 28.16)in the hippocampus,a significant increase over expression in the control group.The Ngb expressions of the EI group were the lowest among the 3 groups-(88.78 ± 18.84) and ( 63.42 ± 16.41 ) in the frontal cortex and hippocampus respectively. Conclusions Early exposure to an enriched environment can increase Ngb expression and improve learning and memory ability,but early isolation will reduce Ngb expression and learning and memory function. Key words: Early environment; Neuroglobin; Learning; Memory

Objective To observe effect of environmental enrichment on the learning and memory ability and the expressions of hypoxia inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in rats with chronic cerebral hypoperfusion. Methods A total of 40 rats were randomly divided into 3 groups: bilateral vascular occlusion (2VO) of the common carotid arteries group (n=14, 2VO group), 2VO + enriched environment (EE) group (n=14, 2VO+ EE group) and sham group (n=12, SHAM group). Morris water maze, novel object recognition test, real-time reverse transcription-polymerase chain reaction (real-time RT-PCR), immunohistochemistry methods and Western blotting were used to detect changes in learning and memory ability of rats and HIF-1α and VEGF expression levels in hippocampus. Results Morris water maze showed that the escape latency was longer in the 2VO group than in the SHAM group at 3, 4 and 5 day during the training (all P<0.05), while the 2VO+ EE group spent significantly less time in finding the platform as compared with the 2VO group at 4 and 5 day (both P<0.05). The time for space exploration in target quadrant was less in 2VO group than in SHAM group (P<0.05), while it was longer in 2VO+ EE group than in 2VO group (P<0.05). Novel object recognition test showed that the 2VO operation impaired the priority index (PI) of time spending at exploring the novel object (P<0.05), and environmental enrichment could improve the PI in 2VO group (P<0.05). The real-time RT-PCR and Western blotting showed that the HIF-1α mRNA expression was higher in 2VO group than in SHAM group (P<0.05). The VEGF mRNA and protein expressions were higher in 2VO+ EE group than in 2VO group (both P<0.05). The expression of HIF-1α in hippocampal CA1 area was higher in 2VO group than in SHAM group (P<0.05). Conclusions Environmental enrichment can alleviate the damages of spatial and non-spatial learning and memory ability which are caused by chronic cerebral hypoperfusion. And HIF-1α and its downstream gene VEGF may be involved in the restoration of cognitive function by enriched environment. Key words: Brain ischemia; Cognition; Milieu therapy; Hypoxia-inducible factor 1; Vascular endothelial growth factor

Many studies have shown that fibronectin type III domain-containing protein 5 (FDNC5) and brain-derived neurotrophic factor (BDNF) play vital roles in plasticity after brain injury. An enriched environment refers to an environment that provides animals with multi-sensory stimulation and movement opportunities. An enriched environment has been shown to promote the regeneration of nerve cells, synapses, and blood vessels in the animal brain after cerebral ischemia; however, the exact mechanisms have not been clarified. This study aimed to determine whether an enriched environment could improve neurobehavioral functions after the experimental inducement of cerebral ischemia and whether neurobehavioral outcomes were associated with the expression of FDNC5 and BDNF. This study established ischemic mouse models using permanent middle cerebral artery occlusion (pMCAO) on the left side. On postoperative day 1, the mice were randomly assigned to either enriched environment or standard housing condition groups. Mice in the standard housing condition group were housed and fed under standard conditions. Mice in the enriched environment group were housed in a large cage, containing various toys, and fed with a standard diet. Sham-operated mice received the same procedure, but without artery occlusion, and were housed and fed under standard conditions. On postoperative days 7 and 14, a beam-walking test was used to assess coordination, balance, and spatial learning. On postoperative days 16-20, a Morris water maze test was used to assess spatial learning and memory. On postoperative day 15, the expression levels of FDNC5 and BDNF proteins in the ipsilateral cerebral cortex were analyzed by western blot assay. The results showed that compared with the standard housing condition group, the motor balance and coordination functions (based on beam-walking test scores 7 and 14 days after operation), spatial learning abilities (based on the spatial learning scores from the Morris water maze test 16-19 days after operation), and memory abilities (based on the memory scores of the Morris water maze test 20 days after operation) of the enriched environment group improved significantly. In addition, the expression levels of FDNC5 and BDNF proteins in the ipsilateral cerebral cortex increased in the enriched environment group compared with those in the standard housing condition group. Furthermore, the Pearson correlation coefficient showed that neurobehavioral functions were positively associated with the expression levels of FDNC5 and BDNF (r = 0.587 and r = 0.840, respectively). These findings suggest that an enriched environment upregulates FDNC5 protein expression in the ipsilateral cerebral cortex after cerebral ischemia, which then activates BDNF protein expression, improving neurological function. BDNF protein expression was positively correlated with improved neurological function. The experimental protocols were approved by the Institutional Animal Care and Use Committee of Fudan University, China (approval Nos. 20160858A232, 20160860A234) on February 24, 2016.

An enriched environment (EE) can stimulate the recovery of neurological function following a cerebral ischaemia-reperfusion injury; however, the impact of EE's on mitochondrial function has been insufficiently studied. Our research aimed to assess whether EE's therapeutic impact involved the enhancement of mitochondrial dysfunction. Following 2 weeks of EE training, we tested both mitochondrial function and mitochondria-associated protein expression within the cerebral cortex following cerebral ischaemia-reperfusion injury. We subjected Sprague-Dawley rats to transient focal cerebral ischaemia and categorized the rats into three separate groups, i.e. an enriched environment (EE) group, a standard condition (SC) group and a sham control group (no middle cerebral artery embolization). The rats within the EE group were raised in enriched conditions for 2 weeks, while the rats within the SC group, in comparison, were reared in standard conditions for 2 weeks. After 2 weeks, the cerebral cortices of the rats were removed. We then measured a series of indices, i.e. the protein expression of peroxisome proliferator-activated receptor gamma coactivator (PGC-1α), nuclear respiratory factor-1 (NRF-1), mitochondrial transcription factor A (TFAM) and mitochondrial protein cytochrome C oxidase subunit IV (COX IV). Furthermore, the number of mitochondria was evaluated through electron microscopy.EE upregulated the protein expression of PGC-1α, NRF-1 as well as TFAM, which function as the master regulators of mitochondrial biogenesis, in comparison with the SC group. The EE group's COX IV protein expression also exhibited an increase. Moreover, the amount of mitochondria in the peri-infarct region of the cortex increased as result of EE training. Over 2 weeks, EE training significantly increased mitochondrial biogenesis-associated protein expression and mitochondrial function. A possible mechanism of the EE leading to the improvement of neurological function is that it increases brain mitochondrial biogenesis after the rats' cerebral ischaemia-reperfusion injury. Mitochondrial biogenesis stimulation or enhancement could become an innovative strategy for neuroprotection in future treatment.

Purpose: The aim of this study was to identify the effects of environmental factors on depressive-like behavior and memory function during adolescence. We performed behavior tests in adolescent rats exposed to environmental enrichment, handling, and social deprivation for eight weeks. Methods: Wistar rats were randomly assigned to control, environmental enrichment, handling, and social deprivation groups at the age of four weeks. Results: In the forced swim test, the immobility time in the environmental enrichment group was decreased than that in the control group (p=.038), while the immobility time in the social deprivation group was increased than that in the control group (p=.035), the environmental enrichment group (p<.001), and the handling group (p=.001). In the Morris water maze test, the social deprivation group had an increased latency time than the control group (p=.013) and the environmental enrichment group (p=.001). In the passive avoidance test, the environmental enrichment group had an increased latency time than the control group (p=.005). However, the social deprivation group had reduced latency time than the socially housed groups (control: p=.030; environmental enrichment: p<.001; handling: p<.001). Conclusion: These findings suggest that environmental factors play an important role in emotion and memory function during adolescence. Key Words: Adolescent; Social environment; Depression; Cognition 국문주요어: ì²­ì†Œë „, ì‚¬íšŒì  환경, 우울, 인지

Effect of enriched environment and predictable chronic stress on spatial memory in adolescent rats: Predominant expression of BDNF, nNOS, and interestingly malondialdehyde in the right hippocampus

Cerebral ischemia activates an endogenous repair program that induces plastic changes in neurons. In this study, we investigated the effects of environmental enrichment on spatial learning and memory as well as on synaptic remodeling in a mouse model of chronic cerebral ischemia, produced by subjecting adult male C57BL/6 mice to permanent left middle cerebral artery occlusion. Three days postoperatively, mice were randomly assigned to the environmental enrichment and standard housing groups. Mice in the standard housing group were housed and fed a standard diet. Mice in the environmental enrichment group were housed in a cage with various toys and fed a standard diet. Then, 28 days postoperatively, spatial learning and memory were tested using the Morris water maze. The expression levels of growth-associated protein 43, synaptophysin and postsynaptic density protein 95 in the hippocampus were analyzed by western blot assay. The number of synapses was evaluated by electron microscopy. In the water maze test, mice in the environmental enrichment group had a shorter escape latency, traveled markedly longer distances, spent more time in the correct quadrant (northeast zone), and had a higher frequency of crossings compared with the standard housing group. The expression levels of growth-associated protein 43, synaptophysin and postsynaptic density protein 95 were substantially upregulated in the hippocampus in the environmental enrichment group compared with the standard housing group. Furthermore, electron microscopy revealed that environmental enrichment increased the number of synapses in the hippocampal CA1 region. Collectively, these findings suggest that environmental enrichment ameliorates the spatial learning and memory impairment induced by permanent middle cerebral artery occlusion. Environmental enrichment in mice with cerebral ischemia likely promotes cognitive recovery by inducing plastic changes in synapses.

Motor disturbances predominantly characterize hypoxic-ischemic encephalopathy (HIE). Among its intervention methods, environmental enrichment (EE) is strictly considered a form of sensory intervention. However, limited research uses EE as a single sensory input intervention to validate outcomes postintervention. A Sprague-Dawley rat model subjected to left common carotid artery ligation and exposure to oxygen-hypoxic conditions is used in this study. EE was achieved by enhancing the recreational and stress-relief items within the cage, increasing the duration of sunlight, colorful items exposure, and introducing background music. JZL184 (JZL) was administered as neuroprotective drugs. EE was performed 21 days postoperatively and the rats were randomly assigned to the standard environment and EE groups, the two groups were redivided into control, JZL, and vehicle injection subgroups. The Western blotting and behavior test indicated that EE and JZL injections were efficacious in promoting cognitive function in rats following HIE. In addition, the motor function performance in the EE-alone intervention group and the JZL-alone group after HIE was significantly improved compared with the control group. The combined EE and JZL intervention group exhibited even more pronounced improvements in these performances. EE may enhance motor function through sensory input different from the direct neuroprotective effect of pharmacological treatment.NEW & NOTEWORTHY Rarely does literature assess motor function, even though it is common after hypoxia ischemic encephalopathy (HIE). Previously used environmental enrichment (EE) components have not been solely used as sensory inputs. Physical factors were minimized in our study to observe the effects of purely sensory inputs.

Early life stress is associated with long-term and pervasive adverse effects on neuroendocrine development, affecting normal cognitive and emotional development. Experimental manipulations like environmental enrichment (EE) may potentially reverse the effects of early life stress induced by maternal separation (MS) paradigm in rodents. However, the functional brain networks involved in the effects of EE after prolonged exposure to MS have not yet been investigated. In order to evaluate possible changes in brain functional connectivity induced by EE after MS, quantitative cytochrome c oxidase (CCO) histochemistry was applied to determine regional brain oxidative metabolism in adult male rats. Unexpectedly, results show that prolonged MS during the entire weaning period did not cause any detrimental effects on spatial learning and memory, including depressive-like behavior evaluated in the forced-swim test, and decreased anxiety-like behavior. However, EE seemed to alter anxiety- and depression-like behaviors in both control and MS groups, but improved spatial memory in the latter groups. Analysis of brain CCO activity showed significantly lower metabolic capacity in most brain regions selected in EE groups probably associated with chronic stress, but no effects of MS on brain metabolic capacity. In addition, principal component analysis of CCO activity revealed increased large-scale functional brain connectivity comprising at least three main networks affected by EE in both MS and control groups. Moreover, EE induced a pattern of functional brain connectivity associated with stress and anxiety-like behavior as compared with non-enriched groups. In conclusion, EE had differential effects on cognition and emotional behavior irrespective of exposure to MS. In view of the remarkable effects of EE on brain function and behavior, implementation of rodent housing conditions should be optimized by evaluating the balance between scientific validity and animal welfare.

To study how motivational factors modulate experience-dependent neurobehavioral plasticity, we modify a protocol of environmental enrichment (EE) in rats. We assumed that the benefits derived from EE might vary according to the level of incentive salience attributed to it. To enhance the rewarding properties of EE, access to the EE cage varied randomly from 2 to 48 h for 30 days (REE). The REE group was enriched only 50% of the time and was compared to standard housing and continuous EE (CEE) groups. As behavioral readout, we analyzed the spontaneous activity and the ultrasonic vocalizations (USVs) within the EE cage weekly, and in the open field test at the end of the experiment. In the cage, REE increased the utilization of materials, physical activity, and the rate of appetitive USVs. In the OF, the CEE-induced enhancements in novelty habituation and social signaling were equaled by the REE. At the neural level, we measured the expression of genes related to neural plasticity and epigenetic regulations in different brain regions. In the dorsal striatum and hippocampus, REE upregulated the expression of the brain-derived neurotrophic factor, its tropomyosin kinase B receptor, and the DNA methyltransferase 3A. Altogether, our results suggest that the higher activity within the cage and the augmented incentive motivation provoked by the REE boosted its neurobehavioral effects equaling or surpassing those observed in the CEE condition. As constant exposures to treatments or stimulating environments are virtually impossible for humans, restricted EE protocols would have greater translational value than traditional ones.

Environmental enrichment-mediated functional improvement after experimental traumatic brain injury is contingent on task-specific neurobehavioral experience

Poststroke cognitive impairment severely affects the long-term recovery of patients. However, it remains unknown whether an enriched environment can remodel contralateral hippocampal function and promote cognitive function recovery after cerebral ischemic injury. To further explore, 36 C57BL/6 mice that underwent permanent middle cerebral artery occlusion (pMCAO) were randomly assigned to three groups: enriched environment (EE), standard condition (SC), and sham surgery (Sham). After 21 days of intervention, the Morris water maze and step-through test was utilized for testing the cognitive function of the mice, cresyl violet staining for measuring the degree of atrophy in the hippocampal tissues, and western blotting for quantitating the expression levels of GA1B, GAD67, and NR2B, and immunohistochemistry for levels of NR2B in the CA1 region of the contralateral hippocampus. The results showed that cognitive function-related behavioral performance decreased in the SC group, and performance was better in the EE group than that in the SC group (p < 0.01); no significant difference in the degree of contralateral cerebral atrophy was observed between the EE and SC groups (p > 0.05); levels of GA1B, GAD67, and NR2B in the contralateral hippocampus were significantly higher in the EE group than those in the SC group (p < 0.01); and the level of NR2B in the CA1 region of the contralateral hippocampus significantly increased in the EE group compared to the SC group (p < 0.01). We believe that contralateral hippocampal function is inhibited after cerebral ischemic injury, further affecting cognitive function. However, enriched environment can upregulate GABAergic and glutamatergic systems in the contralateral hippocampus to promote cognitive function recovery after cerebral ischemic injury.