The Inhibition of State-Dependent Learning Induced By Scopolamine Via Blockade of Dorsal Hippocampal Beta1-Adrenergic Receptors in Rats

Adrenergic and cholinergic systems of the brain play an important role in learning and memory. Previous studies indicate that scopolamine impair inhibitory avoidance memory and induce state-dependent learning. In the present study, the effects of β1-adrenoceptor antagonist on scopolamine state-dependent learning were examined in rat dorsal hippocampus. In this experimental study 155 adult male rats were anaesthetized and cannulae implanted bilaterally in the CA1 regions of the dorsal hippocampus using stereotaxic method. Seven days after recovery from surgery, the behavioral testing was started in inhibitory avoidance task. In this study Scopolamine as muscarininc receptor antagonist and atenolol as β1-adrenergic receptor antagonist were used. Pre-training intra-CA1 injection of scopolamine (1.5 and 3 µg/rat) impaired inhibitory avoidance memory. Amnesia produced by pre-training scopolamine was reversed by pre-test administration of the same dose of scopolamine that is due to a state-dependent effect. Pre-test intra-CA1 injection of atenolol (0.09 μg/rat) also impaired inhibitory avoidance memory. Furthermore, pre-test injection of atenolol (0.09 μg/rat) 2 min before the administration of scopolamine inhibited scopolamine state-dependent memory. It can be concluded that the β1-adrenergic receptors of dorsal hippocampus may play an important role in scopolamine state-dependent learning.