Evaluation of interaction between effects of Hippocampal dopaminergic and Medial septum Gabaergic agents on anxiety-like behavior in wistar rats

The septum and hippocampus act in concert to control anxiety. In the present study, the possible interaction between septal GABAergic and hippocampal dopaminergic systems in the elevated plus-maze test, an animal model of anxiety were examined. We found that a 10-ng infusion of GABAa receptor agonist, muscimol in the medial septum have an anxiolytic effect, whereas lower doses (2.5 and 5.0 ng) did not induce any effect. Micro-infusion of 1 ng/rat of Baclofen, GABAb receptor agonist into the same location decreased open-arm exploration in the elevated plus-maze, but lower doses (0.1 and 0.5 ng) did not. Intra dorsal-hippocampal infusions of dopamine D1/D2 receptor agonist, apomorphine had opposite effects on anxiety- like behavior in dose dependent manner. Lower dose of apomorphine (0.005 µg/rat) increased the percentage of open arm entries and open arm time, whereas higher dose (0.1µg/rat) decreased these parameters,but moderate doses of apomorphine (0.01, 0.05 µg/rat) could not alter the anxiety- like parameters. The infusion of combined sub(non)-effective doses of apomorphine(0.01µg) and muscimol(2.5 ng) significantly reduced anxiety-like behavior, while co-infusion of sub(non)-effective doses of apomorphine and baclofen(0.1 ng) showed an anxiogenesis effect.The results may indicate that the hippocampal dopaminergic and septal gabaergic systems act synergistically in the modulation of anxiety and the involvement of dopamine is dose dependent.