Time window required to elicit a facilitatory effect of previous learning over the performance in a different task

COLETTIS N; SNITCOFSKY M.; GONZÁLEZ N.; KORNISUIK E.; JERUSALINSKY

Huerta Grande-Córdoba, Argentina

Congreso; I Reunión Conjunta de Neurociencias (IRCN); 2009

Taller Argentino de Neurociencias y a la Sociedad Argentina de Investigación en Neurociencias (SAN)

Time window required to elicit a facilitatory effect of previous learning over the performance in a different task Colettis, N1.; Snitcofsky, M1,2.; Gonzalez, N.1.; Kornisiuk, E.1 ; Jerusalinsky, D.1,3 1IBCyN, 2Dept Anatomía, 3CBC, UBA, Argentina. The exposure in two consecutive days, for 3 minutes, to an Open Field (OF) exerted a facilitatory effect on the performance of Wistar rats in a Step Down Inhibitory Avoidance task (IA) (Snitcofsky et al., this session). It is well known that N-Mehyl-D-Aspartate receptors (NMDAR) are involved in synaptic plasticity and related functions, such as learning and memory. To evaluate the role of the NMDAR on this facilitation, we have investigated the effect of an i.p. injection of MK801 (0.07 mg/kg), a non-selective NMDAR blocker given 20 to 30 minutes before the OF test (second exposure), in adult male Wistar rats, on the performance in an IA task. Neither the MK801 injected nor the control group (injected with saline) showed the OF facilitatory effect in the IA performance. Although control animals reached the learning criteria in this task, while treated animals did not, there were not statistically significant differences. On the other hand, the same dose of MK801 injected 20 min before the IA training session, did not affect the OF facilitatory effect over this task. However, at variance with the data reported in the literature, this same dose of the antagonist given 20 min before IA training to rats without previous OF exposure, did not show any significant effect. Preliminary electrophysiologycal assays (Field potentials) in hippocampal brain slices corroborated that MK801 (20 µM) blocked LTP induction at the Schaffer collateral-CA1 cells synapse. In brief, we could not conclude whether the NMDAR is directly involved in this phenomenon, but there would be a relatively short time window lasting 30 to 40 min, when the facilitation is labile enough to be affected by “aversive manipulation” of the animals (injections). However, 20 minutes before training in the IA, the facilitation seems to be established, and neither MK801 nor the manipulation and injection modified this effect.