THE INVESTIGATION OF THE THERAPEUTIC MECHANISMS OF ANTIDEPRESSANT ON NEUROTRANSMITTER RELEASE

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We have molecularly cloned 707 cDNA fragments as expressed sequence tags (ESTs), which we named them antidepressant related genes, ADRG#1-707. Using these cDNAs, we developed our original cDNA microarray for rapid secondary screening of candidate genes as the novel therapeutic targets. With this microarray, we found that the expression of the gene, ADRG#14 was significantly increased in rat frontal cortex which had b*** chronically treated with a selective serotonin reuptake inhibitor antidepressant, sertraline. Sequence analysis o**ADRG#14 with the EMBL/GeneBank database showed significant homology to rat synaptobrevin 2 (VAMP 2) gene. To investigate further the functional roles of endogenous VAMP2 in nerve growth factor (NGF)-differentiated PC12 cells, VAMP2 antibody was transfected to these cels to inhibit the endogeneous VAMP2. Stimulation of the cells with high-[K+] buffer caused a time-dependent elevation of [3H]noradrenaline release in controls. However, this release was significantly and strongly diminished in transfectants. On the other hand, measurement of the morphological changes demonstrated that the mean length of the longest neurite in each cell and the total length of neuiites per cell was significantly shorter in the transfectants, respectively. In addition, the mean neurite number per cell was also significantly smaller in the transfectants. These data indicated that endogenous VAMP2 plays an importanat role not only for neurotransmitter release, but also for neurite outgrowth and sprouting in NGF-differentiated PC12 cells. Previously, we have identified VAMP2 as a novel molecular target for antidepressant. One of the long-term therapeutic action of antidepressant may be related to the changes of both functional and structural neuroplasticity.