Subthreshold synaptic activation of voltage-gated Ca2+ channels mediates a
localized Ca2+ influx into the dendrites of hippocampal pyramidal neurons.
Magee, Jeffrey C., Geri Christofi, Hiroyshi Miyakawa, Brian Christie, Nechama
Lasser-Ross, and Daniel Johnston.
Division of Neuroscience, Baylor College of Medicine, One Baylor Plaza,
Houston, Texas 77030, Department of Physiology, University College London,
Gower Street, London WC1E 6BT. Present address: University of Oxford Clinical
School, John Radcliffe Hospital, Headington, Oxford, OX3 9DU Department of
Cellular Neurobiology, Tokyo University of Pharmacy and Life Sceince, 1432--1
Hironouchi, Hachioji, Tokyo 192--03, Japan, Department of Physiology, New York
Medical College, Valhalla, New York, 10595.
APStracts 2:0181N, 1995.
SUMMARY AND CONCLUSIONS
Whole-cell recordings and high-speed fluorescence imaging were used to
investigate the spatial and temporal characteristics of Ca2+ influx during
synaptic activity in hippocampal CA1 pyramidal neurons. Brief, subthreshold
trains of synaptic potentials elicited by Schaffer collateral stimulation
produced transient increases in [Ca2+ ]i in the apical dendrites near the site
of synaptic input. The rises in [Ca2+ ]i were not due to Ca2+ entry through
NMDA- or nonNMDA-activated glutamate channels, but were reduced by low
concentrations of Ni2+ . Hyperpolarizing prepulses caused an increase in the
synaptically evoked Ca2+ transients, while strong hyperpolarization during the
train prevented the rise in [Ca2+ ]i. The data suggest that subthreshold
synaptic activity can open low-voltage activated (T-type) Ca2+ channels and
produce a local increase in intradendritic [Ca2+ ]. Such local increases in
[Ca2+ ]i may be important for modulating the strength of synaptic connections.
Received 38 March 1995; accepted in final form 30 May 1995.
APS Manuscript Number J202-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.