Effects of gabaergic and morphinergic systems in CA1 nucleus on anxiety and arousal memory based on test-retest paradigm

Hippocampus is a key structure in anxiety processing and memory storage. The purpose of this study was to investigate the interaction between GABAergic systems in CA1 area of hippocampus with morphinergic system in modulating of these behaviors. In this study, male wistar rats were cannulated with stereotaxic surgery in CA1 site. After a recovery period, morphine (µ opioid receptor agonist) was injected intraperitoneal, muscimol and bicuculline (GABAA receptor agonist and antagonist) were injected into the CA1. Parameters such as percentage of Open arms time (%OAT) and entries (%OAE) were calculated by means of an EPM apparatus. One-way ANOVA analysis showed that intraperitoneal administration of morphine increased %OAT and %OAE, indicating the anxiolytic effect of morphine. Based on paired sample T-test, the rate of memory formation improved. Pre-test intra-CA1 infusion of muscimol and bicuculline induced anxiolytic-like and anxiogenic-like behaviors, respectively; meanwhile, both drugs improved memory. Systemic injections of an effective dose of morphine combined with triple doses of muscimol showed a synergistic effect on memory formation and anxiety reduction. Simultaneous injection of morphine and bicuculline altered the negative effects of the latter on anxiety and increased the memory formation. This finding showed that GABAergic and opioidergic systems have similar effects on memory and anxiety in CA1 area.