The effects of hippocampal opioidergic and septal GABAergic system interactions on anxiety-like behavior in rats

Aims: Previous studies have shown that the septum and hippocampus are connected and play a key role in anxiety-related behavior. In the present study, the effects of the interactions between the opioidergic system in the dorsal hippocampus (CA1) and the GABAergic system in the medial septum on anxiety in male Wistar rats were investigated. Main methods: An elevated plus maze was used to study the effects of anxiogenic and anxiolytic drugs in rodents. Male Wistar rats were used for this test. We injected morphine (2.5, 5.0, and 7.5 mu g/rat) into the CA1 and GABA(A) agonist muscimol (2.5, 5.0, and 10.0 ng/rat) into the intra-medial septum (MS). Conversely, we detected the microinjection of bicuculline, a GABAA antagonist (10, 20, and 30 ng/rat), into the MS. OAT%, OAE% and locomotor activity were determined by this behavioral test. Key findings: We found that the simultaneous administration of intra-CA1 morphine (2.5 mu g/rat) and intra-MS muscimol (2.5 ng/rat) increased the magnitude of anxiolysis. On the other hand, simultaneous administration of intra-CA1 morphine (7.5 mu g/rat) and intra-MS bicuculline decreased the anxiolytic effect. Significance: In conclusion, our data suggest that the opioidergic system in the CA1 is involved in anxiety-related behavior and influences the GABAergic system within the MS. In addition, we observed that the interactions between the opioidergic and GABAergic systems within the septohippocarnpus increased anxiety-related behavior compared to stimulation of these receptor systems independently. Crown Copyright (C) 2011 Published by Elsevier Inc. All rights reserved.