Calcium permeability changes and neurotransmitter release in cultured rat brain neurons. I. Effects of stimulation on calcium fluxes

Journal Article · Wed Dec 25 04:00:00 EST 1985 · J. Biol. Chem.; (United States)

OSTI ID:5529169

Yarom, M; Zurgil, N; Zisapel, N

The permeability of neuronal membranes to Ca2+ is of great importance for neurotransmitter release. The temporal characteristics of Ca2+ fluxes in intact brain neurons have not been completely defined. In the present study 45Ca2+ was used to examine the kinetics of Ca2+ influx and efflux from unstimulated and depolarized rat brain neurons in culture. Under steady-state conditions three cellular exchangeable Ca2+ pools were identified in unstimulated cells: 1) a rapidly exchanging pool (t1/2 = 7 s) which represented about 10% of the total cellular Ca2+ and was unaffected by the presence of Co2+, verapamil, or tetrodotoxin; 2) a slowly exchanging pool (t1/2 = 360 s) which represented 42% of the total cellular Ca2+ and was inhibited by Co2+, but not by verapamil or tetrodotoxin; 3) a very slowly exchanging pool (t1/2 = 96 min) which represented 48% of the total cell Ca2+ was observed only in the prolonged efflux experiments. The rate of exchange of 45Ca2+ in the unstimulated cells was dependent on the extracellular Ca2+ concentration (half-saturation at 70 microM). Depolarization of the neurons with elevated K+ causes a rapid and sustained 45Ca2+ uptake. The cellular Ca2+ content increased from 56 nmol/mg protein in unstimulated cells to 81 nmol/mg protein during 5 min of depolarization. The kinetics of the net 45Ca2+ uptake by the stimulated neurons was consistent with movement of the ion with a first order rate constant of 0.0096 s-1 (t1/2 = 72 s) into a single additional compartment. The other cellular Ca2+ pools were apparently unaffected by stimulation. The stimulated 45Ca2+ uptake was inhibited by Co2+ and by the Ca2+ channel blocker verapamil but not by the Na+ channel blocker tetrodotoxin. Ca2+ uptake into this compartment was dependent on the extracellular Ca2+ concentration (half-saturation at 0.80 mM Ca2+).

• OSTI ID: 5529169
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 30; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
560301 -- Chemicals Metabolism & Toxicology-- Cells-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMAL CELLS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BODY
BRAIN
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CELL CONSTITUENTS
CELL CULTURES
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
COBALT
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
METALS
NERVE CELLS
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ORGANS
PERMEABILITY
PHYSICAL PROPERTIES
RADIOISOTOPES
RATS
RODENTS
SOMATIC CELLS
STIMULATION
TRACER TECHNIQUES
TRANSITION ELEMENTS
VERTEBRATES