Effect Of Naloxone On Learning And Memory In Rats With Vascular Dementia And Research Of The Neurobiological Mechanisms

Dementia is a kind of acquired and progressive cognitive dysfunctional syndrome induced by cerebral abnormalities. Vascular dementia (VD) results from the destruction of brain tissue following cerebrovascular disease. VD manifests with insidious and progressive cognition loss, which has not been effectively dealed with by now.The endogenous opioid system plays an important role in cognitive functions and may contribute to the progression of some kind of dementia. The major opioid receptor populations were altered in district area of postmortem brains of Alzheimer disease patients. These results suggest an involvement of the endogenous opioid system in cognitive dysfunction that accompanies the dementia. Naloxone has been shown to exert beneficial effects on memory deficits in patients with senile demintia and reverse some of the effects induced by endogenous opioids. To the best of our knowledge, there has been no report on the effects of naloxone on VD.The hippocampal formation is a crucial element of the neurobiology basis of higher cognitive function. The dysfunction and loss of hippocampal neurons is the pathology basis of congnitive dysfunction that accompanies dementia. Inour study, the effects of naloxone on the behaviour of rats with VD in the Morris water maze were searched for. Then the morphysiology alteration and the apoptosis of hippocampal neurons were studied, and LTP of PS from Schaffer collareral to CA1 regiom pathway in the hippocampal slice preparations was inspected to observe the influence of naloxone on the synaptic plasticity in the hippocampal neuronal network. Then laser scanning confocal microscope (LSCM) was used to investigate the DNA, RNA changes in hippocampal pyramidal neurons. Our findings demonstrate that naloxone could exert beneficial effects on cognitive function in dementia in rats by facilitating the synaptic plasticity, modulating DNA, RNA metabolism and decreasing the apoptosis of hippocampal pyramidal neurons.Materials and methodsMaterials1. Animals:16-month-old aged Sprague-Dawley (SD) male rats, body weight 352.1 23.5g.2. Agents:Naloxone Hydrochloride Injection, Toluidine Blue O, acridine orange, ET radioimmunoassy kit.3. ApparatusVC-11 Memory Oscilloscope; SS-201 J Isolator; SEN-7203 Electronic Stimulator; MEN-8301 Microeletrode Amplifier; H-300 Transmission Eletrone Microscope; ACAS Ultima-312 Laser Scanning Confocal Microscope, FACS 420 flow cytometry. Methods 1. Creation of experiment model:Rats of experimental group were treated with a permanent bilateral common carotid arteries occlusion (2-VO) for establishing vascular dementia model. Rats were randomly divided into three groups viz. the sham operated controls, nontreated VD rats and naloxone treated VD rats.2. MWM assaysThe Morris water maze training comprised three components: hidden platform trials, visible platform trials and probe trials. The Morris water maze test was performed to study the ability of spatial learning and memory.3. Nissl and HE stain:Four consecutive 6- m slices and two 4- m slices were cut to be stained by Toludine Blue O and HE respectively.4. Serum endothelin levelET determination was performed with radioimmunoassy.5. The ultrastructurial altertion in CA1 region of hippocampus: Electronic microscope was employed to observe the ultrastructurialaltertion in CA1 region of hippocampus.6. The apoptosis of hippocampal cellsInvestigating the apoptosis in situ in the brain of rats with a TdT-mediated dUTP nickend labeling (TUNEL) method and electron microscope. Flow cytometry was used to quantified the apoptotic cells.7. Electrophysiological experiments:The potential of PS from Schaffer collateral to CA1 region pathway were recorded in hippocampal slices.8. DNA, RNA metabolism in hippocampal neuronsLaser scanning confocal microscope (LSCM) and Acridine Orange were used to investigate the DNA, RNA changes in hippocampal pyramidal neurons. Statistic analysisAll data were...