The Calcium Homeostasis And Morphology Of Neurons In Vascular Dementia Mice Hippocampus And The Effect Of Huperzine A

Objective:Vascular Dementia (VD) is a common disease that is severely harmful to the physical and mental health of the elderly, as well as a heavy load to the society and family. With the proportion of the elderly in the population increases, the mental and intelligent handicaps caused by cerebral vascular diseases increase. It is significant to study the prevention and cure of VD. At present, its pathogenesis can't be fully explained and the pharmacological mechanism of Huperzine A that can improve intelligence of VD is still in discussion. Hippocampus is considered as the important structure associated with learning and memory. In physical state, Ca2+ in hippocampus neurons, as the second signal, participates in the development of long term potentiation (LTP) that is the microcosmic form of learning and memory. Ischemia and anoxemia affects the calcium channels and calcium pump and calcium binding protein; thus results in calcium over-loading in hippocampus neurons and calcium homeostasis imbalance. In order to explore the molecule pathogenesis of VD and the pharmacological mechanism of Huperzine A improving intelligence, our experiments establish the VD mouse model, observe the resting [Ca2+]i in single hippocampus neuron and its dynamic movement while depolarized, count the neurons, observe its shape and ultrastructure change.Methods:Our study is made up of three sections. Section one is about the establishment of VD model, Kunming mice are subjected continuous repeated ischemia-reperfusion three times through the ligation of the bilateral common carotid arteries, accompanied by sham-operation comparison group and medication group (Huperzine A); the ability of learning and memory of mice are tested by the step-down test and water maze test, and the behaviors are observed after mice have been bred 28 days. Section two is about the single hippocampus neurons acutely dissociated through cold assimilation by the trypsin. Fluo-3/AM as the specific fluorescence dye, the resting [Ca2+]i and dynamic movement in them are observed through laser scanning confocal microscopy (LSCM). They are depolarized by high concentration potassium solution (50 mmol/L), the [Ca2+]i dynamic movement in 300 sec is observed, its ascending peak value and amplitude, and its time during ascending or descending are recorded. These values in every group are compared as well as the dynamic movement curve is drawn. Section three is about the brains fixed up by perfusion of 4% paraformaldehyde solution and dyed through Nissl method or Golgi method respectively. The microcosmic changes of hippocampus are observed through microscopy and neurons of CA1 area are counted comparatively. The changes of apical dendrites and basal dendrites of hippocampal CA1 pyramidal neurons are observed. The ultrastructure change of hippocampal CA1 pyramidal neurons is observed through transmission electron microscopy (TEM).Results: ⑴ Step-down test: The learning and memory ability of model group reduce notably that is reflected by the prolongation of response period (P<0.01) and increase of the error times (P<0.01) during the learning phase, and by decrease of latent period (P<0.01) and increase of the error times (P<0.01) during the memory phase. But the medication group ameliorates apparently, compared with model group (P<0.01), while with sham-operated group has no distinction (P>.05). ⑵ Water maze test: The learning and memory ability of model group also reduce notably that is shown as the prolongation of the whole course time of swimming and increase of the error times during both learning phase (P<0.01) and memory phase (P<0.01). But the medication group ameliorates apparently, compared with model group (P<0.01), while with sham-operated group has no distinction (P>.05). ⑶ Resting [Ca2+]i of hippocampus neuron: [Ca2+]i of model group increases distinctly, compared with sham-operated group(P<0.01); while [Ca2+]i of medication group ameliorates apparently, compared with model group (P<0.01), and with sham-operated group has no difference (...