||Microinjection of Dynorphin into the Hippocampus Impairs Spatial Learning in Rats.
McDaniel, K. L. ;
Mundy, W. R. ;
Tilson., H. A. ;
||Health Effects Research Lab., Research Triangle Park, NC. ;North Carolina State Univ. at Raleigh. ;National Inst. of Environmental Health Sciences, Research Triangle Park, NC. Lab. of Molecular and Integrative Neuroscience.
Dose-response relationships ;
Endogenous substances receptors
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The effect of hippocampal dynorphin administration on learning and memory was examined in spatial and nonspatial tasks. Bilateral infusion of dynorphin A(1-8)(DYN; 10 or 20 micrograms in one microliter) into the dorsal hippocampus resulted in dose-related impairment of spatial working memory in a radial maze win-stay task. Subsequent experiments found that acquisition of a reference memory task in the water maze was impaired by DYN injections (20 micrograms/microliter) in the dorsal hippocampus, but not in the ventral hippocampus, and that this impairment could be blocked by naloxone. In a nonspatial task, posttraining DYN injections in the dorsal hippocampus had no effect on retention of step-through passive avoidance. These results suggest that dynorphin specifically interferes with spatial learning and memory, and that this effect is mediated by opioid receptors in the dorsal hippocampus.