Calcium clamp in single nerve cells.
Free calcium concentration in isolated single neurons was clamped using a new technical approach based on a feed-back connection between the Fura-2 fluorescence signal measuring the intracellular Ca2+ concentration ([Ca2+]i) and iontophoretic current injecting Ca2+ into the cell. Beginning of [Ca2+]i clamping at a level above the basal one triggered fast (few seconds) current transients equal to injection of 36 +/- 20 microM Ca2+ (for a 0.1 microM change of [Ca2+]i), representing the filling of a fast cytosolic buffer. Continuation of clamping required very small clamping currents (corresponding to injection of 0.39 +/- 0.20 microM.s-1 Ca2+). This value increased proportionally to the magnitude of the change of [Ca2+]i above basal level, indicating the activation of calcium-dependent mechanisms for Ca2+ removal from the cytosol. The described approach allowed measurement, under physiological conditions, of the capacitative and kinetic properties of different Ca-regulating systems functioning in a single nerve cell as well as other types of cells.
Belan
P V
PV
Bogomoletz Institute of Physiology, Ukrainian Academy of Sciences, Kiev, Ukraine.
Kostyuk
P G
PG
Snitsarev
V A
VA
Tepikin
A V
AV
D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases; D002451:Cell Compartmentation; D003600:Cytosol / Q000378:metabolism; D005470:Fluorometry; D016257:Fura-2 / Q000378:metabolism; D006372:Helix, Snails / Q000378:metabolism; D007478:Iontophoresis; D008564:Membrane Potentials; D008839:Microelectrodes; D008845:Microinjections; D009474:Neurons / Q000378:metabolism*; D009482:Neurophysiology / Q000295:instrumentation; D009994:Osmolar Concentration
D002021:Buffers; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2