Micromolar Ca2+ transients in dendritic spines of hippocampal pyramidal neurons in brain slice

• Published in: Neuron (Cambridge, Mass.) Mass.), 1995-06, Vol.14 (6), p.1223-1231
• Main Authors: Petrozzino, J J, Pozzo Miller, L D, Connor, J A
• Format: Article
• Language: English
• Subjects: 2-Amino-5-phosphonovalerate - pharmacology; Animals; Calcium - metabolism; Calcium - pharmacology; Culture Techniques; Dendrites - metabolism; Egtazic Acid - pharmacology; Electric Conductivity; Electric Stimulation; Electrophysiology; Fluorescent Dyes; Fura-2 - analogs & derivatives; Hippocampus - ultrastructure; Neurons - metabolism; Potassium Channel Blockers; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate - physiology; Synapses - physiology
• ISSN: 0896-6273
• 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.