Effects of intrahippocampal injections of N-methyl-D-aspartate receptor antagonists and scopolamine on working and reference memory assessed in rats by a three-panel runway task
Ohno, M.; Yamamoto, T.; Watanabe, S.
Journal of Pharmacology and Experimental Therapeutics 263(3): 943-950
1992
ISSN/ISBN: 0022-3565 PMID: 1361577 Document Number: 398922
In order to elucidate the roles of hippocampal N-methyl-D-aspartate-type excitatory amino acid receptors in working and reference memory in rats, the effects of intrahippocampal injections of selective and competitive N-methyl-D-aspartate receptor antagonists such as CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylic acid), 3-(+-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid and 2-amino-5-phosphonovaleric acid on this behavior were examined with a three-panel runway task. The results were compared with the effect of the muscarinic receptor antagonist scopolamine. In the working memory task, CGS 19755 and 3-((+-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid at 10 and 32 ng/side, injected bilaterally into the dorsal hippocampus before testing, produced a significant increase in the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points). This also occurred after the rats were given systemic injection of these drugs at 3.2 and 10 mg/kg. In the reference memory task, neither CGS 19755 nor 3-((+-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid affected the number of errors, whether given at doses up to 32 ng/side intrahippocampally or up to 10 mg/kg systemically. Working memory errors also increased significantly after intrahippocampal injections of d-2-amino-5-phosphonovaleric acid at 100 and 320 ng/side, but were not affected by I-2-amino-5-phosphonovaleric acid at doses up to 1 mu-g/side. On the other hand, intrahippocampal scopolamine at 1.0 and 3.2 mu-g/side increased significantly working memory errors, without affecting reference memory errors. In contrast, systemic administration of scopolamine at 0.32 and 0.56 mg/kg increased significantly both working and reference memory errors. These findings indicate that mechanisms mediated by N-methyl-D-aspartate receptors and muscarinic receptors in the hippocampus are involved in working memory, but not in reference memory.