Radial maze performance in three strains of mice: role of the fimbria/fornix

The excitatory action of quinolinic acid has been examined on neurons in different parts of the rat CNS. When applied by microiontophoresis quinolinic acid excited cells in the cerebral cortex, hippocampus and neostriatum, but even when applied from electrodes which produced responses in these areas, quinolinic acid was ineffective in the cerebellum and spinal cord. Like most excitants tested in other studies, L-glutamate was excitatory to all cells examined. As an endogenous compound, therefore, quinolinic acid may merit special attention as a potential neurotransmitter in brain.     

AChE-positive fiber growth after hippocampal fimbria transection and peripheral nerve homogenate implantation

Gelfoam treated with peripheral nerve homogenate was implanted into a site of hippocampal fimbria transection in the adult rat to assess whether the homogenate might enhance growth of AChE-positive fibers into the lesion site and whether the fiber growth might be directed to the implants. Homogenate was prepared from intact peripheral nerve and in a few cases from degenerated nerve. Some implants were encased in Silastic. Homogenate was also injected into the denervated hippocampus. The major finding was that AChE-positive fiber growth was associated with regions of high astroglial cell content in preference to the relatively hypocellular implants. No clear differences in AChE fiber sprouting into the lesion site, fiber growth into implants, or hippocampal reinnervation were noted between homogenate and saline-treated animals.     

穹窿海马伞切割后海马内NSCs的增殖和向神经元的分化

目的观察切割穹窿海马伞侧和非切割侧大鼠海马内自体神经干细胞的增殖和向神经元分化的情况。方法切割SD大鼠右侧穹窿海马伞,术后2 d腹腔注射BrdU,连续5d,于术后28 d取脑冰冻切片,进行BrdU/NF-200免疫荧光双标检测。结果切割穹窿海马伞侧海马内的BrdU免疫荧光阳性细胞明显多于非切割侧,且发现有BrdU/NF-200双标神经元,而非切割侧未见到BrdU/NF-200双标神经元。结论穹窿海马伞切割后,切割侧海马内自体神经干细胞增殖加快,并可向神经元分化。     

Evidence for reduced dentate gyrus and fimbria volume in bipolar II disorder

Objectives: Dentate gyrus (DG)‐dependent inhibition of the stress response might play an important role in mood disorders. During stress, hippocampal projections traversing the fimbria, a white matter bundle on the hippocampal surface, inhibit the hypothalamic–pituitary–adrenal (HPA) axis. The aim of the present study was to measure the volumes of the DG–cornu ammonis 4 (DG–CA4) and fimbria in patients with bipolar II disorder (BD‐II) and healthy controls using a recently developed magnetic resonance imaging (MRI)‐based technique. Methods: Thirty‐seven individuals with a DSM‐IV diagnosis of BD‐II and 42 healthy controls underwent 3‐Tesla MRI. Hippocampal subfield volumes were estimated using a novel segmentation algorithm implemented in FreeSurfer. Results: In patients with BD‐II there was a significant reduction in the volume of the left [analysis of covariance (ANCOVA), F = 7.84, p = 0.006] and total (left + right) (F = 4.01, p = 0.047) DG–CA4 and left (F = 4.38, p = 0.040) and total (F = 4.15, p = 0.045) fimbria compared to healthy controls. Explorative analyses indicated a smaller left CA2–3 volume in subjects with BD‐II compared to healthy controls, and a reduced left fimbria volume in unmedicated patients compared to medicated patients and controls. Conclusions: Our results provide evidence for the involvement of the DG and fimbria in BD‐II. Longitudinal studies of the DG and fimbria with assessments of the HPA axis in BD‐II are warranted.     

Super-resolution track-density imaging studies of mouse brain: comparison to histology

The recently proposed track-density imaging (TDI) technique was introduced as a means to achieve super-resolution using diffusion MRI. This technique is able to increase the spatial resolution of the reconstructed images beyond the acquired MRI resolution by incorporating information from whole-brain fibre-tracking results. It not only achieves super-resolution, but also provides very high anatomical contrast with a new MRI contrast mechanism. However, the anatomical information-content of this novel contrast mechanism has not yet been assessed. In this work, we perform such a study using diffusion MRI of ex vivo mouse brains acquired at 16.4T, to compare the results of the super-resolution TDI technique with histological staining (myelin and Nissl stains) in the same brains. Furthermore, a modified version of the directionally-encoded colour TDI map using short-tracks is introduced, which reduces the TDI intensity dynamic range, and therefore enhances the directionality colour-contrast. Good agreement was observed between structures visualised in the super-resolution TDI maps and in the histological sections, supporting the anatomical information-content of the images generated using the TDI technique. The results therefore show that the TDI methodology does provide meaningful and rich anatomical contrast, in addition to achieving super-resolution. Furthermore, this study is the first to show the application of TDI to mouse brain imaging: the high-resolution, high-quality images demonstrate the useful complementary information that can be achieved using super-resolution TDI.     

山茱萸环烯醚萜苷对穹隆海马伞切断大鼠海马区神经元存活和细胞凋亡调控因子的影响

目的探讨山茱萸环烯醚萜苷(cornel iridoid glycoside,CIG)对脑损伤大鼠海马区神经元存活的影响及其作用机制。方法 成年SD大鼠行穹隆海马伞切断(fimbria-fornix transection,FFT)手术,造模后CIG灌胃给药28d,采用尼氏染色方法光镜下观察海马CA1区和齿状回存活神经元的变化;采用Western blotting法检测海马区细胞凋亡调控因子Bcl-2、Bax和细胞色素C的蛋白表达变化。结果 尼氏染色结果显示,FFT模型大鼠海马CA1区和齿状回存活神经元明显减少;CIG(20、60、180mg.kg-1)灌胃给药能够增加模型大鼠海马区存活神经元的数量。Western blotting结果显示,FFT模型大鼠海马区Bcl-2表达减少,Bax和细胞色素C表达增高;CIG能够增强模型大鼠海马区Bcl-2表达,抑制Bax和细胞色素C的表达,避免凋亡信号进一步激活。结论 CIG能够减少FFT模型大鼠海马区神经元死亡数量,其作用机制可能与上调细胞凋亡抑制因子、下调细胞凋亡促进因子有关。     

Ladostigil prevents age-related glial activation and spatial memory deficits in rats

Oxidative stress and glial activation occur in the aging brain. Ladostigil is a new monoamine oxidase (MAO) and acetylcholinesterase (AChE) inhibitor designed for the treatment of Alzheimer's disease. It has neuroprotective and antioxidant activities in cellular models at much lower concentrations than those inhibiting MAO or AChE. When ladostigil (1 mg/kg/day) was given for 6 months to 16-month-old rats it prevented the age-related increase in activated astrocytes and microglia in several hippocampal and white matter regions and increased proNGF immunoreactivity in the hippocampus towards the levels in young rats. Ladostigil also prevented the age-related reduction in cortical AChE activity and the increase in butyrylcholinesterase activity in the hippocampus, in association with the reduction in gliosis. The immunological and enzymatic changes in aged rats were associated with improved spatial memory. Ladostigil treatment had no effect on memory, glial or proNGF immunoreactivity in young rats. Early treatment with ladostigil could slow disease progression in conditions like Alzheimer's disease in which oxidative stress and inflammatory processes are present.