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Ca 2+ ‐Dependent Enhancement of [ 3 H]Dopamine Uptake in Rat Striatum: Possible Involvement of Calmodulin‐Dependent Kinases
Author(s) -
Uchikawa Tomoyoshi,
Kiuchi Yuji,
Yura Akihiko,
Nakachi Noriyuki,
Yamazaki Yukako,
Yokomizo Chie,
Oguchi Katsuji
Publication year - 1995
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1995.65052065.x
Subject(s) - striatum , calmodulin , dopamine , chemistry , kinase , neuroscience , biophysics , biology , biochemistry , enzyme
We studied effects of Ca 2+ in the incubation medium on [ 3 H]dopamine ([ 3 H]DA) uptake by rat striatal synaptosomes. Both the duration of the preincubation period with Ca 2+ (0–30 min) and Ca 2+ concentration (0–10 m M ) in Krebs‐Ringer medium affected [ 3 H]DA uptake by the synaptosomes. The increase was maximal at a concentration of 1 m M Ca 2+ after a 10‐min preincubation (2.4 times larger than the uptake measured without preincubation), which reflected an increase in V max of the [ 3 H]DA uptake process. On the other hand, [ 3 H]DA uptake decreased rapidly after addition of ionomycin in the presence of 1 m M Ca 2+ . The Ca 2+ ‐dependent enhancement of the uptake was still maintained after washing synaptosomes with Ca 2+ ‐free medium following preincubation with 1 m M Ca 2+ . Protein kinase C inhibitors did not affect apparently Ca 2+ ‐dependent enhancement of the uptake, whereas 1‐[ N,O ‐bis(1,5‐isoquinolinesulfonyl)‐ N ‐methyl‐ l ‐tyrosyl]‐4‐phenylpiperazine (KN‐62; a Ca 2+ /calmodulin‐dependent kinase II inhibitor) and wortmannin (a myosin light chain kinase inhibitor) significantly reduced it. Inhibitory effects of KN‐62 and wortmannin appeared to be additive. N ‐(6‐Aminohexyl)‐5‐chloro‐1‐naphthalenesulfonamide hydrochloride (W‐7; a calmodulin antagonist) also remarkably inhibited the enhancement. These results suggest that Ca 2+ ‐dependent enhancement of [ 3 H]DA uptake is mediated by activation of calmodulin‐dependent protein kinases.