Novel environment and cat odor change GABA and 5-HT release and uptake in the rat

In hippocampal and cortical slices taken from rats moved in their home cages to a novel environment for 5 min, there were decreases in basal and K(+)-evoked [14C]GABA release and an increased [14C]GABA uptake compared with slices taken from rats remaining undisturbed in the animal house. The changes in 5-hydroxytryptamine (5-HT) release and uptake in response to a novel environment were markedly time dependent. In rats killed immediately after the 5-min exposure, there was decreased hippocampal [3H]5-HT uptake and higher hippocampal basal release, whereas in rats killed 30 min later there was increased [3H]5-HT uptake and lower basal release in both hippocampal and cortical slices. Rats exposed to cat odor in the novel environment showed increased release and decreased uptake of GABA in both brain areas compared with the group exposed to a neutral odor in the same novel environment, and these differences between the two odor groups were found both immediately and 30 min after the odor exposure. In contrast, only one measure of 5-HT function differed between the neutral and cat odor groups, with the latter showing increased cortical [3H]5-HT uptake 30 min after odor exposure.