Evaluation of memory and anxiety in rats observed in the elevated plus-maze: effects of age and isolation

Abstract

Twenty young (5 months) and 20 old (20-24 months) male Wistar rats, isolated or group housed, were tested in the elevated plus-maze to evaluate memory and anxiety. Memory was quantified by transfer latency (the time it took for the rat to move from the open arm to the enclosed arm) and anxiety by percent entries into the open arms. Isolation decreased the transfer latency of old (session 1 = 119.33 +/- 0.44 s; session 3 = 49.67 +/- 12.12 s) and young (session 1 = 111.20 +/- 8.80 s; session 3 = 55.90 +/- 13.60 s) rats, but did not modify percent entries into the open arms (old-isolated = 5.56 +/- 5.56; old-group housed = 10.18 +/- 7.05; young-isolated = 35.16 +/- 8.98; young-group housed = 33.21 +/- 8.11). Conversely, aging decreased percent entries into the open arms but did not affect the transfer latency of isolated or group-housed animals. The results indicate that the plus-maze test, unlike other methods for memory evaluation, does not discriminate between young and old rats. They also suggest that age increases anxiety and that isolation increases memory levels, but that there is no interaction between age and isolation with regard to their effect on memory and anxiety in rats.