Mutsuko Maekawa1,#, Satoshi Ono2,
Hirokazu Narita2, Toshihiko Murayama1 and Yasuyuki
Nomura1,*
1Departmentof Pharmacology, Graduate School of Pharmaceutical
Sciences, Hokkaido University, Sapporo 060ﾐ0812, Japan
2ResearchLaboratories, Toyama Chemical Co., Ltd., Toyama 930ﾐ8508,
Japan
#Present address: Research Laboratories,
Toyama Chemical Co., Ltd., Toyama 930ﾐ8508, Japan
*To whom correspondence should be addressed.
Abstract: Previously, we reported that (R)ﾐ(-)ﾐ1ﾐ(benzo[b]thiophenﾐ5ﾐyl)ﾐ2ﾐ[2ﾐ(N,Nﾐdiethylamino)ethoxy]ethanol
hydrochloride (Tﾐ588), a novel putative cognitive enhancer, stimulated noradrenaline
(NA) release from rat cerebral cortical slices. In this study, we investigated
the effects of Tﾐ588 compared to other secretagogues on NA release from
PC12 cells. Addition of as little as 10 microM Tﾐ588 stimulated [3H]NA
release in a doseﾐdependent and an extracellular Ca2+ﾐindependent
manner from PC12 cells. Ten micromolar ionomycinﾐ, 300 microM adenosineﾐ5'ﾐOﾐ(gammaﾐthiotriphosphate)ﾐ
and 10 microM forskolinﾐinduced extracellular Ca2+ﾐdependent
[3H]ﾐNA release was further enhanced by 30 microM Tﾐ588. Cytosolic
synaptophysin and 25ﾐkDa synaptosomeﾐassociated protein immunoreactivity
was increased by addition of Tﾐ588 in a doseﾐdependent manner. Interestingly,
increases in synaptic vesicleﾐrelated proteins triggered by Tﾐ588 had a
4ﾐmin lag time and were completely dependent on extracellular CaCl2.
These findings suggest that Tﾐ588 stimulates NA release from PC12 cells
in a Ca2+ﾐindependent manner. Tﾐ588 also induced the translocation
of synaptic vesicles in a Ca2+ﾐdependent manner.
Keywords: Tﾐ588, Noradrenaline release, Synaptic vesicle, Synaptophysin,
PC12 cell