M Torras-García | PubMed Health

PubMed1994

Long-term memory facilitation in rats by posttraining epinephrine.

Effects of posttraining epinephrine (EPI) on retention of a massed (1 session, 30 trials) 2-way active avoidance task in rats were studied. The rats received an injection (ip) of 0.05 mg/kg EPI, 0.01 mg/kg EPI, or distilled water immediately after the training session. EPI did not improve retention 24 hr after the training session (Experiment 1) but enhanced retention 20 days after the training session (Experiment 2). The group receiving the smaller dose of EPI had better retention than the group receiving the larger dose, indicating dose dependency. The authors suggest that the process of consolidation of massed 2-way active avoidance conditioning is long and elaborative. Posttraining EPI would facilitate this active process of consolidation, improving performance as consolidation goes on. This facilitation needs, at least under certain conditions, more than 24 hr to be expressed as a higher level of performance on the retention test.

Animals↗

PubMed1993

Facilitation of a distributed shuttlebox conditioning with post-training epinephrine in rats.

Forty-two male Wistar rats were trained in a two-way active avoidance task during 5 consecutive days (10 trails/session). Immediately after each training session animals were given an injection, ip, of 0.1 mg/kg (EPI 0.1 group) or 0.05 mg/kg (EPI 0.05 group) of epinephrine, or vehicle (Vehicle group). Long-term retention was tested 20 days after the last acquisition session. Our results showed that the lower dose of epinephrine (0.05 mg/kg) led to a significant improvement of acquisition, compared with both the Vehicle and the EPI 0.1 group. On the long-term retention session the level of avoidances in both EPI 0.05 and Vehicle groups was similar to that achieved on the last acquisition session, although differences between groups failed to reach statistical significance. Concerning the EPI 0.1 group, a significant increase in the number of avoidances was observed between the last acquisition session and the long-term retention session. This later result might suggest that the higher dose of epinephrine would need a longer period to manifest its effectiveness. We conclude that the facilitatory effects of epinephrine are dose-dependent, and that under a distributed paradigm epinephrine modulates memory consolidation processes leading to an improvement of the magnitude of learning rather than merely speeding up learning.

Animals↗