SOCIAL-INTERACTION AND ELEVATED PLUS-MAZE TESTS - CHANGES IN RELEASE AND UPTAKE OF 5-HT AND GABA

Changes in release and uptake of [H-3]5-HT and [C-14]GABA were compared in slices taken from the hippocampus and frontal cortex of rats, left undisturbed in their home-cages, or exposed for 5 min to the elevated plus-maze or social interaction tests of anxiety. Exposure to the plus-maze decreased cortical GABA function (shown by decreased release) and increased hippocampal 5-HT function (shown by increased K+-evoked release but more markedly by decreased uptake). Compared with undisturbed home cage controls, only the high light, familiar condition of the social interaction test resulted in a significant increase in K+-evoked release of both [H-3]5-HT and [C-14]GABA from the hippocampus. All four social interaction test conditions resulted in increases in cortical uptake of [H-3]5-HT and all but the high fight, unfamiliar condition increased cortical uptake of [C-14]GABA. Analysing the two factors manipulated in the social interaction test, unfamiliarity with the test arena resulted in increased uptake of hippocampal [H-3]5-HT and decreased cortical [C-14]GABA, whereas an increase in the level of light decreased the cortical uptake of [C-14]GABA. The results show that changes in presynaptic function occur rapidly in response to a brief exposure to animal tests of anxiety. However, only the increased hippocampal release of 5-HT is likely to be causally linked to anxiety and the results show that this cannot be the sole explanation.