INTRAHIPPOCAMPAL ADMINISTRATION OF LEAD (PB) IMPAIRS PERFORMANCE OF RATS IN THE MORRIS WATER MAZE

We examined spatial learning in the Morris water maze after daily acut e bilateral micro-injection of 13.9 ng sodium acetate (NaAc) or 37.9 n g lead acetate (PbAc) in 1 mu l volumes into the dorsal hippocampus of normal adult rats. After six days of injections and water maze traini ng, rats injected with NaAc were able to find a hidden platform in 8.3 s, and those injected with PbAc were significantly slower (15.2 s; p < 0.02). In a second experiment, rats were trained to find a hidden pl atform before injections began and then tested in order to determine i f intrahippocampal injections of Pb affected the recall of a previousl y learned task. The escape latency on the first day after injections b egan was increased slightly when compared to the last day of training before injections, however the NaAc and PbAc groups were not significa ntly different over three days of injections. Both treatment groups pe rformed as well as they did before injections began by the second day of injections. These results suggest that the direct injection of Pb i nto the hippocampus impairs the acquisition, but not the recall of the spatial learning task in the Morris water maze. (C) 1997 Elsevier Sci ence Inc.