Regulation of DARPP-32 phosphorylation at Thr-34 and Thr-75 by dopamine
via D1- and D2-type receptors in neostriatum. (a) Effect
of dopamine on the level of phospho-Thr-34 and phospho-Thr-75 DARPP-32.
Slices were incubated with dopamine (100 μM) in the presence of a
dopamine uptake inhibitor, nomifensine (10 μM), for the indicated
times. Immunoblots are shown (Upper) for the detection
of phospho-Thr-34 (Left) and phospho-Thr-75
(Right), using phosphorylation state-specific antibodies
and the same nitrocellulose membrane. Quantitative results, normalized
to values obtained with untreated slices, are shown below each blot.
A.U., arbitrary units. Data represent means ± SEM for four
experiments. **, P < 0.01 compared
with 0 min; †, P < 0.05 compared with 6 min,
Student's t test. (b) Regulation of
DARPP-32 phosphorylation at Thr-34 (Left) and Thr-75
(Right) by dopamine D1 and D2 receptor agonists and
antagonists. Data are shown for untreated neostriatal slices (Con) and
slices treated with a D1 agonist, SKF81297 (SKF) (1 μM); a D1
antagonist, SCH23390 (SCH) (1 μM); a D2 agonist, quinpirole (Quin) (1
μM); and a D2 antagonist, raclopride (Rac) (1 μM), as indicated.
Data represent means ± SEM for 5–15 experiments. *,
P < 0.05, **, P
< 0.01 compared with control; ††, P < 0.01
compared with SKF81297 alone; §§, P < 0.01
compared with quinpirole alone, Student's t test.
(c) Effect of SCH23390 and raclopride on dopamine
regulation of DARPP-32 phosphorylation on Thr-34 (Left)
and Thr-75 (Right). Data are shown for treatment of
neostriatal slices with dopamine (100 μM), SCH23390 (1 μM), and
raclopride (1 μM), as indicated. Data represent means ± SEM for
five experiments. **, P < 0.01
compared with control; ††, P < 0.01 compared
with dopamine alone, Student's t test.