Effect Of Murine Cytomegalvirus Infection On Learning, Memory And The Role Of CaMKII In Its Mechanism

[Objective] To establish MCMV-infected murine model and observe the learning-memorizing ability of adult mice infected by MCMV in childhood.[Methods] We infected murine embryonic fibroblast cells with murine cytomegalovirus and measured infectivity by viral titer. Newborn BALB/c mice and their mother were randomly separated into MCMV-infected group and control group. Newborn mice were intracerebrally inoculated with MCMV suspension with a microsyringe in the first 24-hour after birth. The controls were injected with 0.9% natrii chloride of equal volume. 3 months later, the capability of learning and memorizing of two groups were tested by Morris water maze.[Results] The learning-memorizing ability of MCMV-infected group significantly decreased than the control(P<0.01). Conclusion MCMV infection could lead to the neural dysfunction and debasement of learning-memorizing ability of inoculated mice. [Objective] To observe the change of Ca²⁺/CaM/ CaMKII levels in the MCMV-infected murine brain and probe into the neurobiological pathogenesis of brain dysfunction owing to MCMV infection.[Methods] The MCMV-infected group and the control group wereseperated into five subgroups, respectively. The [Ca²⁺]_i in the hippocampus neurons of the first subgroup was measured by fluorescent spectrophotometer; total RNA of the second subgroup, known as RT-PCR subgroup, was extracted and the mRNA level of CaM was assayed; the memberane proteins of the hippocampus in the third subgroup, known as Western-blotting subgroup, were extracted and the change of CaMKII in the membrane of neurons were recorded.The fourth group, mitochondria transmembrane potentials was measured by means of flow cytometry (FCM). The fifth group,Analyze quantitatively the thickness of PSD and the width of synaptic cleft in the hippocampal CA3 under the electron microscope.[Results] In the MCMV-infected group, the [Ca²⁺]_i in the hippocampusneurons were higher than the controls, and the mRNA level of CaM in the hippocampus was increased, while the CaMKII in the membrane decreased. Mitochondria transmembrane potentials in the infected group was decreased.The control group's relative level of PSD was thicker than infected group's and the width of synaptic cleft in the hippocampal CA3 was narrower. All the difference were statistically significant(P<0.01).[Conclusion] Changes in the Ca²⁺/CaM/ CaMKII system could be caused by MCMV infection. The learning-memorizing ability could be indirectly reflected by the change of CaMKII, which is the molecular basis of space-learning and memory. Changes in the Ca²⁺/CaM/ CaMKII system might play an role in the mechanism of brain dysfunction and reducing memory induced by MCMV infection.Part IIIEffect of MCMV infection on the astrocytes and GFAP level of the neuroglial cellsAbstract[Objective] To observe the effects on the glial fibrillary acidic protein of astrocytes of MCMV-infected murine hippocampus and to analyze the relationship between the changes of hippocampal astrocytes and learning-memorizing ability.[Methods] The murine model was established as stated before. 3 months later, the MCMV-infected group and the control group were divided into two subgroups, respectively. The level of GFAP mRNA and protein were assayed by RT-PCR and immunohistochemistry.[Result] In the MCMV-infected group, the GFAP mRNA increased as exposed by RT-PCR, while astrocytes expressing GFAP positively in the CA1 region and CA3 region were significantly more than control group(P<0. 01). Shape of glial cells also changed a lot :hypertrophy of cell's body and thick and long process.[Conclusion] The changes of GFAP levels and the morphology of astrocytes in the MCMV-infected murine hippopotamus might contribute to the pathogenesis of learning-memorizing disorders in the mice.