| 其他摘要 | Behavioral stress can either block or facilitate learning and memory, inhibited the induction of long-term potentiation (LTP) and facilitated long-term depression (LTD). However, the relevance of the stress experience dependent LTD (SLTD) to spatial learning and memory task was unknown; also, the effect of stress on age-related synaptic plasticity in vivo was primarily known; we even didn't know why stress either enhanced or impaired spatial memory under different conditions.In the first part, we investigated the effects of acute and sub-acute elevated platform (EP) and footshock (FS) stress on LTD induction in CA1 region of the hippocampus in anesthetized 4 weeks old Wistar rats and spatial memory in Morris water maze (a useful model of spatial learning and memory). The results showed that: (1) LTD was facilitated by acute but not sub-acute EP stress; but FS stress facilitated LTD induction both in acute and sub-acute treatment. (2) Acute EP stress impaired the spatial memory but the sub-acute EP stressed animals performed the spatial memory task as well as the controls; however, acute FS stress did not affect the spatial memory, and sub-acute FS even enhanced the spatial memory retrieval. Our findings exhibited that the effect of stress on spatial memory was disassociated with the effect of stress on LTD, but was associated with the stress experience and the stress types (EP or FS). Thus, SLTD may relate to certain stress memory. March 18~22, 2002 and dust storm process during April 13-17, 2002 that sand and dust emissions in modeling area in these two processes are weak in west area and strong in east area. On the west of 95°E, there are disperse dust emissions only around Taklimakan Desert and the vertical dust fluxes are not too large, so this region only is a weak dust source area during these two dusty weather processes, which are consist with concerned observational data. On the east of 100°E, dust emission areas in these two processes are very wide and their intensities are very high, which is consistent with the phenomenon reflected by observational data concerned; at the same time, prevailing wind in this region are west or westerly, leading that dusts suspended in air are easily transported eastwardly and arousing far and wide dusty weather, therefore, this region should be a main dust source area in these two processes. On the south of 40°N and between 90°E~100°E, sand and dust emissions are also always high and vertical dust fluxes even exceed lO^kgnfV1. However, the simulated results in these two processes are not consistent with observational results of visibility completely, so this region is likely to be a bogus dust source area, and the possible reasons lie in that the modeled friction velocities are on the high side and the surface data is not proper.(6), from the point of molded factors, during the intense dust storm process between March 18 and 22 of 2002, spatial variations and distributions of intensity of sand and dust emissions are mainly influenced by friction velocity. Surface relative humidity and threshold friction velocity are minor factors. While the dust storm process between April 13 and 17 of 2002 is companied with a precipitation process in north China, inducing large variations in temporal and spatial of surface relative humidity, and resulting in that both surface relative humidity and friction velocity are main factors influencing sand and dust emissions, and secondary factor is threshold friction velocity. In addition, from the point of comparison with observational data, modeling effect of intense dust storm is better than that of general dust storm. |
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