The Influence Of Amphetamine On Learning And Memory, Synaptic Structure And Synaptophysin Expression In Rats

Objective: To study the influence of amphetamine on spatial learning and memory, synapticsrtructure and synaptophysin expression at hippocampal formation in rats.Methods: SD rats were randomly divided into three groups: swimming group,saline group andamphetamine group. (1)swimming group swam in the same deep water and in the same temperature as amphetamine group; (2) saline group was injected the same dose of saline as amphetamine group; (3) amphetamine group was injected 0.5mg/kg amphetamine once a day. The ability of spatial learning and memory were assayed with water maze. The rats were killed at 14 d, 28 d and 42 d. The quality and quantity of synaptophysin expression were studied between different phrases and groups by immunohistochemistry and Western blotting. The morphology change of synapse formation was observed by the transmission electron microscope.Results:(1) Influence of amphetamine on ability of spatial learning and memory: There was an obvious reduction during learning and memory for average latent and average running time between saline group and amphetamine group at 14 d (P <0.05). There was an obvious reduction for right rate between saline group and amphetamine group at 28 d (P <0.05). And there was an obvious increase for right rate and running time between amphetamine and saline groups at 42 d (P <0.05).(2)Distribution of SYN positive granules in hippocampal formation: There was an tendency that the expression of SYN in amphetamine group in CA1 and CA2 region decreased than CA3 and CA4 region on hippocampal formation in rats. And there was no obvious difference in layers in every region.(3)Quantity of SYN expression in hippocampal formation: There was an obvious reduction of SYN expression between amphetamine group and swimming group at 28 d and 42 d(P <0.05). And there was an obvious reduction of SYN expression at 42 d than 14 d in amphetamine group(P <0.05).(4)The ultrastructure observation of vertebra cell layer in CA3 region in hippocampal formation: The synaptic structure is unclear in amphetamine group. The presynaptic memebrane was thickener in amphetamine group than swimming group. Medullary sheath was loose and abrubted in amphetamine group.Conclusion: ntramuscular injection of 0.5mg/kg amphetamine once everyday degraded thecapability of spatial learning and memory after 28 d in rats; reduced the expression of SYN and damaged the synaptic structure at CA3 sub region in hippocampal formation. These damages were aggravated at 42 d.