Genetic differences in response to novelty and spatial memory using a two-trial recognition task in mice

A two-trial memory task, based on a free-choice exploration paradigm in Y-m aze, was previously developed to study recognition processes in Sprague-Daw ley rats. Because this paradigm avoids the use of electric shock or depriva tion that may have nonspecific effects and does not require learning of a r ule, it may be particularly useful for studying memory in mice. Four inbred strains (Balb/cByJ, DBA/2J, C57BL/6J, and SJL/J), an Fl hybrid (C57BL/b x SJL/J), and one outbred strain (CD1) were used to validate this task in mic e and to characterize a strain distribution in response to novelty and work ing memory. Exploration was measured with a short (2 min) intertrial interv al (ITI) between acquisition and retrieval, while memory was examined with longer intervals (30 min, 1 h, and 2 h). A study of the time course of the response to novelty revealed varying degrees of preference and/or habituati on to novelty among the different strains, with CD1 exhibiting a very high response to novelty and others showing lower (C57 x SJL hybrids) to complet e absence (SJL) of exploration of novelty. Memory span, assessed with incre asing ITIs, varied widely among strains from 30 min (C57 x SJL hybrids) to at least 2 h (C57 and BALE). Such demonstrated sensitivity to a wide range of behavioral phenotypes supports the use of this spatial memory task as an effective tool for the study of genetic influences on the response to nove lty and recognition processes in mice. (C) 2000 Academic Press.