Abstract
The relationship between the free cytoplasmic Ca2+ concentration, [Ca2+](i), and neurotransmitter release was investigated in guinea pig brain synaptosomes and the neurosecretory cell line PC12. Release was induced by α-latrotoxin, which acts in both Ca2+-containing and Ca2+-free incubation media, or by the classical depolarizing agents high K+ and veratridine, which require extracellular Ca2+. Two complementary approaches were used to reveal changes of [Ca2+](i): (i) direct measurement by a fluorescent Ca2+ indicator (quin2) and (ii) study of the Ca2+-dependent phosphorylation of a protein, synapsin I, located at the cytoplasmic surface of synaptic vesicles. Depolarizing agents, when applied in Ca2+-containing medium, induced the [Ca2+](i) to increase promptly 3- to 6-fold, drastically increased synapsin I phosphorylation, and caused stimulation of transmitter release. With α-latrotoxin, the [Ca2+](i) increase was delayed and occurred at a slower rate, the increase of synapsin I phosphorylation was less drastic, and the release response was much more pronounced. In Ca2+-free medium, depolarizing agents released no transmitter and had no effect on [Ca2+](i) or synapsin I phosphorylation, whereas with α-latrotoxin these processes were dissociated: considerable stimulation of the release without apparent change of [Ca2+](i) and synapsin I phosphorylation. We conclude that the relationship between average [Ca2+](i) and transmitter release is not straightforward and, in particular, that the release evoked by α-latrotoxin in Ca2+-free medium is mediated by a factor(s) other than bulk redistribution of Ca2+ from intracellular stores.
| Original language | English |
|---|---|
| Pages (from-to) | 620-624 |
| Number of pages | 5 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 81 |
| Issue number | 2 I |
| Publication status | Published - 1984 |
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ASJC Scopus subject areas
- General
- Genetics
Cite this
Free cytoplasmic Ca2+ and neurotransmitter release : Studies on PC12 cells and synaptosomes exposed to α-latrotoxin. / Meldolesi, J.; Huttner, W. B.; Tsien, R. Y.; Pozzan, T.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 81, No. 2 I, 1984, p. 620-624.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Free cytoplasmic Ca2+ and neurotransmitter release
T2 - Studies on PC12 cells and synaptosomes exposed to α-latrotoxin
AU - Meldolesi, J.
AU - Huttner, W. B.
AU - Tsien, R. Y.
AU - Pozzan, T.
PY - 1984
Y1 - 1984
N2 - The relationship between the free cytoplasmic Ca2+ concentration, [Ca2+](i), and neurotransmitter release was investigated in guinea pig brain synaptosomes and the neurosecretory cell line PC12. Release was induced by α-latrotoxin, which acts in both Ca2+-containing and Ca2+-free incubation media, or by the classical depolarizing agents high K+ and veratridine, which require extracellular Ca2+. Two complementary approaches were used to reveal changes of [Ca2+](i): (i) direct measurement by a fluorescent Ca2+ indicator (quin2) and (ii) study of the Ca2+-dependent phosphorylation of a protein, synapsin I, located at the cytoplasmic surface of synaptic vesicles. Depolarizing agents, when applied in Ca2+-containing medium, induced the [Ca2+](i) to increase promptly 3- to 6-fold, drastically increased synapsin I phosphorylation, and caused stimulation of transmitter release. With α-latrotoxin, the [Ca2+](i) increase was delayed and occurred at a slower rate, the increase of synapsin I phosphorylation was less drastic, and the release response was much more pronounced. In Ca2+-free medium, depolarizing agents released no transmitter and had no effect on [Ca2+](i) or synapsin I phosphorylation, whereas with α-latrotoxin these processes were dissociated: considerable stimulation of the release without apparent change of [Ca2+](i) and synapsin I phosphorylation. We conclude that the relationship between average [Ca2+](i) and transmitter release is not straightforward and, in particular, that the release evoked by α-latrotoxin in Ca2+-free medium is mediated by a factor(s) other than bulk redistribution of Ca2+ from intracellular stores.
AB - The relationship between the free cytoplasmic Ca2+ concentration, [Ca2+](i), and neurotransmitter release was investigated in guinea pig brain synaptosomes and the neurosecretory cell line PC12. Release was induced by α-latrotoxin, which acts in both Ca2+-containing and Ca2+-free incubation media, or by the classical depolarizing agents high K+ and veratridine, which require extracellular Ca2+. Two complementary approaches were used to reveal changes of [Ca2+](i): (i) direct measurement by a fluorescent Ca2+ indicator (quin2) and (ii) study of the Ca2+-dependent phosphorylation of a protein, synapsin I, located at the cytoplasmic surface of synaptic vesicles. Depolarizing agents, when applied in Ca2+-containing medium, induced the [Ca2+](i) to increase promptly 3- to 6-fold, drastically increased synapsin I phosphorylation, and caused stimulation of transmitter release. With α-latrotoxin, the [Ca2+](i) increase was delayed and occurred at a slower rate, the increase of synapsin I phosphorylation was less drastic, and the release response was much more pronounced. In Ca2+-free medium, depolarizing agents released no transmitter and had no effect on [Ca2+](i) or synapsin I phosphorylation, whereas with α-latrotoxin these processes were dissociated: considerable stimulation of the release without apparent change of [Ca2+](i) and synapsin I phosphorylation. We conclude that the relationship between average [Ca2+](i) and transmitter release is not straightforward and, in particular, that the release evoked by α-latrotoxin in Ca2+-free medium is mediated by a factor(s) other than bulk redistribution of Ca2+ from intracellular stores.
UR - http://www.scopus.com/inward/record.url?scp=0021298128&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0021298128&partnerID=8YFLogxK
M3 - Article
C2 - 6141561
AN - SCOPUS:0021298128
VL - 81
SP - 620
EP - 624
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 2 I
ER -