Mutsuko Maekawa1,#, Satoshi Ono2,
Hirokazu Narita2, Toshihiko Murayama1 and Yasuyuki
1Departmentof Pharmacology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060–0812, Japan
2ResearchLaboratories, Toyama Chemical Co., Ltd., Toyama 930–8508, Japan
#Present address: Research Laboratories, Toyama Chemical Co., Ltd., Toyama 930–8508, Japan
*To whom correspondence should be addressed.
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 microM T–588 stimulated [3H]NA release in a dose–dependent and an extracellular Ca2+–independent manner from PC12 cells. Ten micromolar ionomycin–, 300 microM adenosine–5'–O–(gamma–thiotriphosphate)– and 10 microM forskolin–induced extracellular Ca2+–dependent [3H]–NA release was further enhanced by 30 microM 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.
Keywords: T–588, Noradrenaline release, Synaptic vesicle, Synaptophysin, PC12 cell