[Assessment of effects of alpha2-adrenoceptor agonists and antagonists in dorsal hippocampus on muscimol state-dependent memory]

ABSTRACT

Adrenergic and GABAergic systems of the brain play an important role in memory and learning. According to results of studies, morphine, histamine, and lithium induce state-dependent learning. This study was conducted aiming at assessing the effects of alpha2-adrenergic receptors of CA1 on muscimol state-dependent learning. In this study, Clonidine as agonist and yohimbine as antagonist of alpha2-adrenergic receptor, muscimol as agonist of GABAA receptor and step-through inhibitory avoidance task as a model of learning were used for memory assessment. The data analyzed using one-way analysis of variance, t-test, and Mann-Whitney test. In all statistical assessments, p<0.05 was considered as significance level in the comparison of the groups. Pre-test intra-CA1 injection of muscimol [1.2microg/mice] impaired inhibitory avoidance memory on the test day [p<0.01]. Pre-test injection of muscimol [0.06 and 1.2microg/mice] reversed the memory impaired under pre-training muscimol [1.2microg/mice]; so, muscimol can induce state-dependent learning [p<0.001]. Pre-training injection of Clonidine [0.6 and 1.2microg/mice] also reversed pre-training muscimol [1.2microg/mice, intra-CA1] induced amnesia [p<0.01]. Also pre-test intra-CA1 injection of yohimbine [1.2 and 2.4microg/mice] 2 minutes before administration of effective dose of muscimol inhibited muscimol state-dependent memory [p<0.01]. Overall, It can be conceded that alpha2-adrenergic receptors of dorsal hippocampus have an important role in muscimol state-dependent learning on the test day