Exposure to ethanol during the rat brain growth spurt: Characterizing the learning and memory deficits using variations of the Morris water maze.

摘要

This thesis addressed the specific nature of learning and memory deficits following exposure to ethanol during the rat brain growth spurt (∼human 3rd-trimester).; Experiment 1 extended upon previous work using the delayed matching-to-place (DMP) version of the water maze. This task entails a series of problems, each including search and recall trials that require rats to use extra-maze cues to locate a hidden escape platform. The results confirmed a delay-dependent retention deficit in the ET group as shown by longer swimming distances than controls on the ‘recall’ trials following 2-h, but not 60-s, delays after search trials. This finding indicated a relatively greater deficit in memory for recent events than reference memory.; Experiment 2 investigated whether manipulations aimed at the encoding stage of information processing might improve the performance of ET rats on the DMP. In addition, this experiment assessed the separate and combined effects of ethanol and nicotine, as these drugs are often co-abused.; Experiment 3 addressed the specificity of learning impairment in ET rats through the investigation of possible deficits on a non-spatial visual-discrimination task. Rats were trained to learn either that a horizontally, but not vertically, striped pedestal provided escape from the water maze (H+) or the reverse condition (V+).; Experiment 4 extended the findings of spatial-learning impairment in ET rats to place learning based on the configuration of three visually distinct intra-maze cues, a paradigm in which visual-perceptual demands are minimal.; In conclusion, these findings support an overall deficit with respect to memory for recent problem-specific events, but not for invariant task demands (reference memory), in male rats exposed to high levels of ethanol during the brain growth spurt. This result is consistent with the presence of hippocampal dysfunction and suggests that remedial strategies aimed at improving the encoding of information may prove valuable in ameliorating memory impairment in humans affected by early ethanol insult. (Abstract shortened by UMI.)