Abstract
Ca2+ uptake was measured in purified rat cerebral cortex synaptosomes (P3 pellets) using45Ca2+ as a tracer. Ca2+ influx increased in time, and with an increase in external K+ concentration and temperature. The net (external K+-induced, depolarization-dependent) uptake follows a two-component course. The exponential term, due to the opening of voltage-operated calcium channels (VOC), has a rate constant which increases with an increase in the depolarization level (1.04 versus 0.54 nmol/s/mg protein for 50 mM-versus 15 mM [K+]-dependent net influx). The linear term, due to the Na+/Ca2+ exchange system, has a similar rate constant at all depolarization levels (0.16+/-0.05 and 0.11+/-0.02 nmol/s/mg protein). Excitatory amino acids (glutamate, kainate and n-methyl-d-aspartate-NMDA-) were tested on this preparation at doses ranging between 5×10-5 M and 5×10-3M and at multiple incubation times, under resting conditions and under two depolarizing conditions (partial depolarization: 15 mM external K+ and maximal depolarization: 50 mM external K+). NMDA was also tested in the absence of Mg2+. No effect was detectable under any of these experimental conditions. Hypotheses to interpret these data are discussed. Further studies on other preparations are needed in order to directly investigate the presynaptic effects of excitatory amino acids.
| Original language | English |
|---|---|
| Pages (from-to) | 677-682 |
| Number of pages | 6 |
| Journal | Neurochemical Research |
| Volume | 14 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 1 1989 |
| Externally published | Yes |
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Keywords
- calcium fluxes
- glutamate
- kainate
- NMDA
- Synaptosomes
ASJC Scopus subject areas
- Neuroscience(all)
- Biochemistry
Cite this
Lack of excitatory amino acid-induced effects on calcium fluxes measured with45Ca2+ in rat cerebral cortex synaptosomes. / Simonato, Michele; Jope, Richard S; Bianchi, Clementina; Beani, Lorenzo.
In: Neurochemical Research, Vol. 14, No. 7, 01.07.1989, p. 677-682.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Lack of excitatory amino acid-induced effects on calcium fluxes measured with45Ca2+ in rat cerebral cortex synaptosomes
AU - Simonato, Michele
AU - Jope, Richard S
AU - Bianchi, Clementina
AU - Beani, Lorenzo
PY - 1989/7/1
Y1 - 1989/7/1
N2 - Ca2+ uptake was measured in purified rat cerebral cortex synaptosomes (P3 pellets) using45Ca2+ as a tracer. Ca2+ influx increased in time, and with an increase in external K+ concentration and temperature. The net (external K+-induced, depolarization-dependent) uptake follows a two-component course. The exponential term, due to the opening of voltage-operated calcium channels (VOC), has a rate constant which increases with an increase in the depolarization level (1.04 versus 0.54 nmol/s/mg protein for 50 mM-versus 15 mM [K+]-dependent net influx). The linear term, due to the Na+/Ca2+ exchange system, has a similar rate constant at all depolarization levels (0.16+/-0.05 and 0.11+/-0.02 nmol/s/mg protein). Excitatory amino acids (glutamate, kainate and n-methyl-d-aspartate-NMDA-) were tested on this preparation at doses ranging between 5×10-5 M and 5×10-3M and at multiple incubation times, under resting conditions and under two depolarizing conditions (partial depolarization: 15 mM external K+ and maximal depolarization: 50 mM external K+). NMDA was also tested in the absence of Mg2+. No effect was detectable under any of these experimental conditions. Hypotheses to interpret these data are discussed. Further studies on other preparations are needed in order to directly investigate the presynaptic effects of excitatory amino acids.
AB - Ca2+ uptake was measured in purified rat cerebral cortex synaptosomes (P3 pellets) using45Ca2+ as a tracer. Ca2+ influx increased in time, and with an increase in external K+ concentration and temperature. The net (external K+-induced, depolarization-dependent) uptake follows a two-component course. The exponential term, due to the opening of voltage-operated calcium channels (VOC), has a rate constant which increases with an increase in the depolarization level (1.04 versus 0.54 nmol/s/mg protein for 50 mM-versus 15 mM [K+]-dependent net influx). The linear term, due to the Na+/Ca2+ exchange system, has a similar rate constant at all depolarization levels (0.16+/-0.05 and 0.11+/-0.02 nmol/s/mg protein). Excitatory amino acids (glutamate, kainate and n-methyl-d-aspartate-NMDA-) were tested on this preparation at doses ranging between 5×10-5 M and 5×10-3M and at multiple incubation times, under resting conditions and under two depolarizing conditions (partial depolarization: 15 mM external K+ and maximal depolarization: 50 mM external K+). NMDA was also tested in the absence of Mg2+. No effect was detectable under any of these experimental conditions. Hypotheses to interpret these data are discussed. Further studies on other preparations are needed in order to directly investigate the presynaptic effects of excitatory amino acids.
KW - calcium fluxes
KW - glutamate
KW - kainate
KW - NMDA
KW - Synaptosomes
UR - http://www.scopus.com/inward/record.url?scp=0024386294&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0024386294&partnerID=8YFLogxK
U2 - 10.1007/BF00964878
DO - 10.1007/BF00964878
M3 - Article
C2 - 2571097
AN - SCOPUS:0024386294
VL - 14
SP - 677
EP - 682
JO - Neurochemical Research
JF - Neurochemical Research
SN - 0364-3190
IS - 7
ER -