TIME-PLACE LEARNING IN A COMPLEX ENVIRONMENT IN RATS WITHOUT FOOD RESTRICTION

LAMARCK A ; SANTANA KS; PAULINO C; ARAÚJO JF; VALENTINUZZI VS

Natal, RN, Brasil

Congreso; II Simpósio do Instituto Internacional de Neurociência de Natal-IINN; 2007

Instituto Internacional de Neurociência de Natal-IINN

Time-place learning is the capacity of organisms to associate both space and time with a biological relevant stimulus such as food. Experiments are usually done with food restricted animals due to the belief that food system activation is necessary for time-place learning. Another line of thought suggests that, in addition to food system activation, response cost should be increased to effectively allow time-place discrimination. The purpose of this experiment was to test whether a complex environment, which presumably implied in a heightened response cost, would facilitate time-place association in satiated rats using a highly palatable food as reward. Nine 3-week old Wistar rats kept in a light-dark cycle were used. Animals were handled daily by the experimenters immediately after weaning and during the whole experimental phase in order to habituate the animals and in this way decrease stress. A large experimental box (1mt x 1mt) divided in four compartments was used.  To access each compartment the animals had to overcome a series of obstacles such as ramps, staircases and mazes. Animals were place in the experimental chamber in two 10-min daily sessions in the following conditions. Pre-Training: free exploration of the chamber. No reward Training: Feeder A offered the reward during the ZT09 sessions while feeder D during the ZT15 sessions (30 days). Testing: No reward (1 day). During training the animals showed a clear preference for the correct feeder during the correct time of day expressed by a lower latency to access the rewarded feeder. During the testing days, in which no reward was present, this tendency was maintained however at ZT19 the data was not significant. These results suggest that even satiated animals may be capable of learning a time-space task as far as the experimental context is complex enough to result in a higher response cost. We also suggest that the extreme care to avoid stress using an extensive manipulation phase plus very young animals may have facilitated the formation of time-place discrimination.   Financial support: CNPq, FAPERN.