Petrozzino J J, Pozzo Miller L D, Connor J A
Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110, USA.
Neuron. 1995 Jun;14(6):1223-31. doi: 10.1016/0896-6273(95)90269-4.
The magnitude and dynamics of [Ca2+] changes in spines and dendrites of hippocampal CA1 pyramidal neurons have been characterized using a low affinity fluorescent indicator, mag-Fura 5, that is sensitive to Ca2+ in the micromolar range. During tetanic stimulation (1 s), we observed progressive [Ca2+] increases in distal CA1 spines to as much as 20-40 microM, both in organotypic slice culture and acute slice. Similar accumulations were reached during continuous depolarization (+10 mV, 1 s) when K+ channels had been blocked, but not with spike trains driven by postsynaptic current injection. The large [Ca2+] increases due to tetanic stimulation were blocked by APV, indicating that NMDA receptor-dependent influx was critical for the large responses. These findings have significant implications for low affinity Ca(2+)-dependent biochemical processes and show a new upper limit for [Ca2+] changes measured in these neurons during stimulation.
