Analysis of motor function in 6-month-old male and female 3xTg-AD mice

The Adverse Effects of Auditory Stress on Mouse Uterus Receptivity and Behaviour

Stress during gestation has harmful effects on pregnancy outcome and can lead to spontaneous abortion. Few studies, however, have addressed the impact of gestational stress, particularly auditory stress, on behavioural performance and pregnancy outcome in mice. This study aimed to examine the effect of two types of gestational stress on uterus receptivity and behavioural performance. Pregnant C57BL/6 mice were randomly assigned to either auditory or physical stress conditions or a control condition from gestational days 12-16. The auditory stress regimen used loud 3000 Hz tone, while the physical stressor consisted of restraint and exposure to an elevated platform. Three behavioural tests were performed in the dams after weaning. Uterine receptivity was investigated by counting the number of sites of implantation and fetal resorption. Also, the offspring survival rates during the early postnatal period were calculated. Auditory stress caused an increase in anxiety-like behaviour, reduced time spent exploring new object/environment, and reduced balance when compared to the physical stress and control groups. Auditory stress also caused higher rates of resorbed embryos and reduction of litter size. Our results suggest that the adverse effect of noise stress is stronger than physical stress for both uterus receptivity and behavioural performance of the dams.

Targeted deletion of GD3 synthase protects against MPTP-induced neurodegeneration

Parkinson's disease is a debilitating neurodegenerative condition for which there is no cure. Converging evidence implicates gangliosides in the pathogenesis of several neurodegenerative diseases, suggesting a potential new class of therapeutic targets. We have shown that interventions that simultaneously increase the neuroprotective GM1 ganglioside and decrease the pro-apoptotic GD3 ganglioside - such as inhibition of GD3 synthase (GD3S) or administration of sialidase - are neuroprotective in vitro and in a number of preclinical models. In this study, we investigated the effects of GD3S deletion on parkinsonism induced by 1-methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP was administered to GD3S-/- mice or controls using a subchronic regimen consisting of three series of low-dose injections (11 mg/kg/day × 5 days each, 3 weeks apart), and motor function was assessed after each. The typical battery of tests used to assess parkinsonism failed to detect deficits in MPTP-treated mice. More sensitive measures - such as the force-plate actimeter and treadmill gait parameters - detected subtle effects of MPTP, some of which were absent in mice lacking GD3S. In wild-type mice, MPTP destroyed 53% of the tyrosine-hydroxylase (TH)-positive neurons in the substantia nigra pars compacta (SNc) and reduced striatal dopamine 60.7%. In contrast, lesion size was only 22.5% in GD3S-/- mice and striatal dopamine was reduced by 37.2%. Stereological counts of Nissl-positive SNc neurons that did not express TH suggest that neuroprotection was complete but TH expression was suppressed in some cells. These results show that inhibition of GD3S has neuroprotective properties in the MPTP model and may warrant further investigation as a therapeutic target.

Neuroprotective effects of Chrysophanol against inflammation in middle cerebral artery occlusion mice

Ischemia/reperfusion (I/R) involves a cascade of reactions which ultimately lead to neuronal apoptosis or death. Inflammation plays an important role in this cascade. Chrysophanol (CHR), a purified active constituent from rhubarb, possesses many biological activities including anti-inflammation. The present study investigated the long-term neuroprotective effects of CHR on focal ischemic brain injury and the potential mechanism. Mice were subjected to 45-min middle cerebral artery occlusion and received either vehicle or CHR at 0.1, 1 or 10mg/kg for 14days after reperfusion. Neurological function, survival rate, brain tissue loss, expression of pro-inflammatory factors tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and nuclear factor-kappa B p65 (NF-κB p65) were then assessed. The results showed that treatment with CHR led to improved survival rate and reduced brain tissue loss compared with vehicle-treated mice, accompanied by improved neurological assessment and motor function, which were sustained for 14days after I/R. I/R-induced expression of TNF-α, IL-1β and NF-κB p65 in neurons was markedly reduced in CHR-treated mice. These results indicate that CHR markedly attenuates brain injury after focal I/R, which is attributed at least in part to its anti-inflammatory actions.

Increased Spontaneous Central Bleeding and Cognition Impairment in APP/PS1 Mice with Poorly Controlled Diabetes Mellitus

Alzheimer’s disease (AD) and vascular dementia (VaD) are the most common causes of dementia, and borderlines are blurred in many cases. Aging remains the main risk factor to suffer dementia; however, epidemiological studies reveal that diabetes may also predispose to suffer AD. In order to further study this relationship, we have induced hypoinsulinemic diabetes to APPswe/PS1dE9 (APP/PS1) mice, a classical model of AD. APP/PS1 mice received streptozotocin (STZ) ip at 18 weeks of age, when AD pathology is not yet established in this animal model. Cognition was evaluated at 26 weeks of age in the Morris water maze and the new object discrimination tests. We observed that STZ-induced episodic and working memory impairment was significantly worsened in APP/PS1 mice. Postmortem assessment included brain atrophy, amyloid-beta and tau pathology, spontaneous bleeding, and increased central inflammation. Interestingly, in APP/PS1-STZ diabetic mice, we detected a shift in Aβ soluble/insoluble levels, towards more toxic soluble species. Phospho-tau levels were also increased in APP/PS1-STZ mice, accompanied by an exacerbated inflammatory process, both in the close proximity to senile plaque (SP) and in SP-free areas. The presence of hemorrhages was significantly higher in APP/PS1-STZ mice, and although pericytes and endothelium were only partially affected, it remains possible that blood-brain barrier alterations underlie observed pathological features. Our data support the implication of the diabetic process in AD and VaD, and it is feasible that improving metabolic control could delay observed central pathology.

Early detection of cognitive deficits in the 3xTg-AD mouse model of Alzheimer's disease

Which behavioral test is the most sensitive for detecting cognitive deficits in the 3xTg-AD at 6.5 months of age? The 3xTg-AD mouse model of Alzheimer's disease (AD) has three transgenes (APPswe, PS1M146V, and Tau P301L) which cause the development of amyloid beta plaques, neurofibrillary tangles, and cognitive deficits with age. In order to determine which task is the most sensitive in the early detection of cognitive deficits, we compared male and female 3xTg-AD and B6129SF2 wildtype mice at 6.5 months of age on a test battery including spontaneous alternation in the Y-Maze, novel object recognition, spatial memory in the Barnes maze, and cued and contextual fear conditioning. The 3xTg-AD mice had impaired learning and memory in the Barnes maze but performed better than B6129SF2 wildtype mice in the Y-Maze and in contextual fear conditioning. Neither genotype demonstrated a preference in the novel object recognition task nor was there a genotype difference in cued fear conditioning but females performed better than males. From our results we conclude that the 3xTg-AD mice have mild cognitive deficits in spatial learning and memory and that the Barnes maze was the most sensitive test for detecting these cognitive deficits in 6.5-month-old mice.