Tomoyuki Ono, Isao Matsuoka (*), Satoko Ohkubo, Junko Kimura and Hironori
Nakanishi
Department of Pharmacology, Fukushima Medical College, Hikarigaoka 1,
Fukushima 960-1295, Japan
(*) To whom correspondence should be addressed.
Abstract: Effects of YT-146 [2-(1-octynyl) adenosine], an adenosine
A2 receptor agonist, on cAMP production and noradrenaline (NA)
release were investigated in PC12 cells. YT-146 caused a concentration-dependent
cAMP accumulation (EC50: 1.2+/-O.9 nM). In [3H]NA-prelabeled
cells, YT-146 increased the basal NA release and enhanced ATP-evoked NA
release in a concentration-dependent manner (EC50: 0.23+/-0.15
nM). YT-146 augmented the maximal response to ATP without affecting the
EC50 value of ATP. These effects of YT-146 were inhibited by
several adenosine receptor antagonists with a characteristic of adenosine
A2A receptor subtype. The effects of YT-146 were mimicked by
forskolin, dibutylyl cAMP and Sp-cAMPS, and inhibited by H-89, a cAMP-dependent
protein kinase inhibitor. YT-146 had little effect on ATP-induced increase
in intracellular Ca2+ concentration. YT-146 enhanced the NA release
induced by several different stimuli including Ca2+ ionophore
A23187. The present results suggest that YT-146 is a potent agonist on adenosine
A2A receptors in PC12 cells and causes a cAMP-dependent enhancement
of NA release by affecting the exocytosis process at a point downstream
of the intracellular Ca2+ increase.
Keywords: YT-146, Adenosine A2A receptor, Noradrenaline release,
cAMP, PC 12 cell