Differential basis of strain and rearing effects on open-field behavior inFawn Hooded and Wistar rats

Open-field behavior was examined under several conditions in isolation-rear ed, and socially reared, Fawn Hooded (FH) and Wistar rats. Lighting conditi ons (red or white light) and complexity (object or no object) were varied: Experiment 1, white light, no object; Experiment 2, red light, no object; E xperiment 3, white light, object; Experiment 4, red light, object. ii-he pl asma corticosterone (CORT) response to open-field exposure was examined two further experiments. Observation of differences in open-field behavior, re sulting from strain or rearing condition, was dependent on both lighting co ndition and complexity. Differences in exploratory behavior exhibited by is olation-reared rats were best explained by changes in response to novelty, while those in FH, relative to Wistar, rats were primarily due to increased anxiety. Supporting these conclusions, FH rats had enhanced stimulated COR T levels, while isolation rearing was without effect. (C) 2000 Elsevier Sci ence Inc. All rights reserved.