Two Open Field expositions facilitate performance in an Inhibitory Avoidance task.

SNITCOFSKY M.; COLETTIS N; BLANCO, C.; KORNISUIK E.; JERUSALINSKY D.

Huerta Grande-Córdoba

Taller; I Reunión Conjunta de Neurociencias; 2009

Taller Argentino de Neurociencias y a la Sociedad Argentina de Investigación en Neurociencias

We have studied the performance of adult Wistar rats in a Step Down Inhibitory Avoidance (IA) task, with or without postweaning handling. IA consists in recording training and test latencies to step down onto a grid, from an isolated platform, avoiding a mild footshock. The rats were trained with different footshock intensities (0.4, 0.5, 0.6, 0.75, 1 or 1.5 mA). Learning criteria was reached with 0.5mA or higher for  males, and with 0,75mA for females, with postweaning handling. We then evaluated the influence of an Open Field (OF) on performance of male rats in the IA, with or without handling. Rats were exposed to an OF for 3 min in two consecutive days; 1 hour after the second session they were trained in IA (with either 0.75mA or 1mA); the test session was performed 24h later. Rats that were not previously trained in the OF were also evaluated. All groups reached the learning criteria. Those with handling, that were trained and tested in the OF, showed a significantly better performance in the IA (trained with 1 mA), compared with those that were not exposed to the OF; and they performed even better than those with handling without OF exposure. Moncada &Viola (2007) had reported a promotor effect of a novel enviroment over the IA performance, which was absent in animals exploring a familiar environment. However, our results have shown that the facilitatory effect was there after two OF exposures, 24 h apart. There was a facilitatory effect on the IA after the second OF, while the periodic handling alone did not produce any significant change. None of the above described effects were seen with a 0.75 mA footshock. In conclusion, the learning of a mild or non aversive task (OF), tested 60 min before the IA appeared to facilitate learning of a stronger aversive and associative  task. Therefore, further experiments are required to evaluate whether the responsible for such facilitation was related to the fact that, during the second session of the OF there is still some novelty there or both sessions in the OF are actually required.