Stimulation of Noradrenaline Release by T-588, a Cognitive Enhancer, in PC12 Cells

Abstract

Previously, we reported that(R)−(−)−1−(benzo[b]thiophen−5−yl)−2−[2−(N, N−diethylamino)ethoxy]ethanol hydrochloride(T−588), a novel putative cognitive enhancer, stimulated noradrenaline(NA)release from rat cerebral cortical slices.In this study, we investigated the effects of T−588 compared to other secretagogues on NA release from PC12 cells.Addition of as little as 10 μM T−588 stimulated [³H]NA release in a dose−dependent and an extracellular Ca²⁺−independent manner from PC12 cells.Ten micromolar ionomycin−, 300 μM adenosine−5′−O−(γ−thiotriphosphate)− and 10 μM forskolin−induced extracellular Ca²⁺−dependent [³H]−NA release was further enhanced by 30 μM T−588.Cytosolic synaptophysin and 25−kDa synaptosome−associated protein immunoreactivity was increased by addition of T−588 in a dose−dependent manner.Interestingly, increases in synaptic vesicle−related proteins triggered by T−588 had a 4−min lag time and were completely dependent on extracellular CaCl₂.These findings suggest that T−588 stimulates NA release from PC12 cells in a Ca²⁺−independent manner.T−588 also induced the translocation of synaptic vesicles in a Ca²⁺−dependent manner.