Confocal imaging of dendritic Ca2+ transients in hippocampal brain slices during simultaneous current- and voltage-clamp recording.
Changes in the intracellular Ca2+ concentration ([Ca2+]i) within CA1 hippocampal pyramidal neurons were imaged using confocal laser scanning microscopy in conjunction with Ca(2+)-sensitive fluorescent indicators. The imaging was performed in thick hippocampal brain slices while simultaneously measuring or controlling electrical activity with sharp microelectrodes or whole-cell patch-clamp electrodes. The combination of imaging and electrophysiology was essential for interpreting the changes in [Ca2+]i. We compared the increases in [Ca2+]i produced by either of two methods--direct depolarization of the cell via the somatic electrode or high-frequency stimulations of synaptic inputs. The increases in [Ca2+]i in the soma and proximal dendrites caused by both methods were of comparable magnitude and they always decayed within seconds in healthy cells. However, the spatial patterns of distal Ca2+ increases were different. Separate sets of synaptic inputs to the same cell resulted in different spatial patterns of [Ca2+]i transients. We isolated and observed what appeared to be a voltage-independent component of the synaptically mediated [Ca2+]i transients. This work demonstrates that the combination of neurophysiology and simultaneous confocal microscopy is well suited for visualizing and analyzing [Ca2+]i changes within highly localized regions of neurons in thick brain slices. The approach should allow further analysis of the relative contribution of voltage- and agonist-dependent influences on [Ca2+]i within neurons throughout the CNS and it raises the possibility of routinely relating subcellular [Ca2+]i changes to structural and functional modifications.
Jaffe
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DB
Department of Psychology, Yale University, New Haven, Connecticut 06520.
Brown
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TH
D000375:Aging / Q000378:metabolism; D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D003712:Dendrites / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D004558:Electric Stimulation; D005456:Fluorescent Dyes; D006624:Hippocampus / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D008297:Male; D008839:Microelectrodes; D018613:Microscopy, Confocal; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D009930:Organic Chemicals; D018408:Patch-Clamp Techniques; D011712:Pyramidal Tracts / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure; D014743:Videotape Recording; D014966:Xanthenes
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D009930:Organic Chemicals; D014966:Xanthenes; C071336:calcium green; C059715:Fluo-3; D002118:Calcium