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Background: Ample evidence indicated that
glucocorticoids, when administered after training, enhance memory consolidation
in a variety of tasks. The mechanisms underlying the enhancing effects of
glucocorticoids on memory consolidation are not well known. The aim of this
study was to determine the role of NMDA
receptors and calcium channels in glucocorticoid-induced enhancement of avoidance
memory consolidation in mice.
Methods: Experiments
were performed on 166 male albino mice (about 30gr).
The animals were trained in an inhibitory avoidance (IA) task
(0.5mA shock for 3
seconds). In Experiment 1, dose- response effects of corticosterone on
memory consolidation were determined. Immediately after training in IA task,
the animals were received different doses of corticosterone (0.3, 1 or 3mg/kg).
In Experiments 2 and 3,
effects of corticosterone on memory consolidation were examined in the presence
or absence of verapamil, a calcium channel blocker, (2.5, 5 or 20mg/kg)
or MK-801, an antagonist of NMDA
receptor (0.1mg/kg), respectively. In all experiments, retention
test was done two days later.
Results: Results
from first experiment revealed that corticosterone at dose of 0.3mg/kg
significantly improved consolidation of avoidance. Data from experiments 2 and 3
showed that both verapamil, in doses of 2.5 and 5mg/kg,
and MK801 significantly blocked corticosterone-induced enhancement
of memory consolidation.
Conclusion: Finding of this study clearly
demonstrated that the memory enhancing effects of corticosterone, at least in
part mediate via calcium channels and NMDA receptors.
