Studies On The Spatial Learning And Memory Function In The Marginal Division Of Rat Striatum And Its Mechanism

Learning and memory are the most important functions in the brain. Learning is gaining and development of experiences; memory is keeping and reappearance of experience. They are two different, but closely related neurobiological processes. A new subdivision "marginal division" ,was found located at the caudal most edge of the neostriatum, near the rostral border of the globus pallidus in the brains of rat. cat. monkey and human by Shu SY. MrD consists of fusiform neurons and is densely packed by SP. L-ENK-. NT. SOM and TH positive somata and fibers. The PHA-L labeled efferent fibers of the MrD project to the caudal most part of the globus pallidus near the basal nucleas of Meynert. The striatonigral fibers from the maginal division terminate at the caudal extent of the sbstantia nigra. MrD was proved to be involved in learning and memory function of rat brain by a double blinded Y-maze avoidance task, and the expression of immediate-early genes c-fos and c-jun was observed in the MrD of rat striatum immediately after the Y-maze avoidance training. MrD was proved involving in the auditory digital working memory in human. Also, the lesions in human MrD might cause disorder of cognitive function. There are many types of learning and memory. Spatial learning and memory is an important type of learning and memory which is used popularly, and it is also a type of declarative memory. Dementia is related to declarative memory. So the study of relationship of spatial memory and MrD is important for further understanding the function of MrD. The hippocampus has been popularly regarded as an area playing an important role in spatial learning and memory, thus to investigate the relationship between MrD and hippocampus would help to know the function of the MrD. Nowadays Morris water maze is a popularly used tool to study-7-the spatial learning and memory function of rat. In part one of this study, the fimbria fornix of the rat brain was transected and the marginal division was microinjected with kainic acid to study the difference between the contributes of the MrD and the hippocampus to spatial learning and memory function using Morris water maze to understand the contribute of the MrD to spatial learning and memory neuronal circuit of the brain.The study on molecular mechanism is important to understand the spatial learning and memory function of rat. it was proved that long-term memory needs new proteins, and PKA-CREB signal transduction plays an important role in synthesis process of new proteins. In this signal transduction, signals from outside of cells could enhance concentration of the second messenger cAMP, and then PKA holoenzyme decomposes to catalytic subunits and regulatory subunits. The catalytic subunits then were transferred into cell nucleus and phosphorylate CREB. pCREB will influence synthesis of new proteins. It has been proved that PKA ?CREB signal transduction is assosiated with the spatial learning and memory function .In part two of this study immunohistochemical technique and western blotting which followed with band scanning were used to investigate whether PKA-CREB signal transduction is assosiated with the spatial learning and memory function of MrD, and the relationship between PKA and CREB.Methods and ResultsPart one: comparative study on the spatial learning and memory function between the MrD and hippocampus in ratsChemically destroyed bilateral MrD or transected bilateral fornix/fimbria (FF) were performed in the rat brains. The performance of four group rats on spatial learning and memory during Morris water maze training were investigated 7 days after surgical operation. Firstly, the performance of four group rats on average escape latency during nine blocks of place navigation training were tested. Then the numbers of crossing platform were tested at theafternoon the day the last block of place navigation training were tested and 7days later to investigate maintenance of long term memory. The results exhibited: Both two treated groups had significantly increased in escape la...