Hebbian Induction of LTP in visual cortex: A perforated patch-clamp study
in cultured neurons.
Otsu, Yo, Fumitaka Kimura and Tadaharu Tsumoto.
Department of Neurophysiology, Biomedical Research Center, Osaka University
Medical School, Yamadaoka, Suita 565 JAPAN.
APStracts 2:0211N, 1995.
SUMMARY AND CONCLUSIONS
1.To see whether presynaptic activation paired with postsynaptic
depolarization is necessary for the induction of long-term potentiation (LTP)
in visual cortex or an activation of postsynaptic receptors in conjunction
with depolarization is just sufficient, we carried out perforated patch-clamp
recordings with nystatin from cultured cortical neurons of rats. 2. Recorded
neurons were either monosynaptically activated by electrical stimulation of an
adjacent neuron or by direct activation of glutamate to "hot spots" of
dendrites through iontophoresis or pressure ejection. In experiments in which
cultured neurons were stained immunohistochemically with antibody against
synaptophysin after electrophysiological recordings, "hot spots" were found to
correspond to probable synaptic sites. 3. Excitatory postsynaptic currents
(EPSCs) evoked by test stimulation applied to the adjacent neuron at 0.1 Hz
were recorded at the holding potential of -60 or -70 mV for 5-10 min after an
establishment of whole-cell recording configuration. Then, stimulation was
paired with postsynaptic depolarization (0 mV for 200 ms) at 1 Hz for 30 or 60
s. LTP of EPSCs was induced in 7 of the 15 cells from which stable recordings
were obtained for 18-30 min after pairing. 4. When postsynaptic depolarization
was paired with direct glutamate application in the absence of presynaptic
stimulation in 12 cells, none of them except one showed LTP. Postsynaptic
depolarization alone did not induce LTP in any of the 6 cells tested. Also,
presynaptic stimulation alone did not induce LTP in any of the 5 cells tested.
5. These results suggest that the concurrent activation of presynaptic
elements with postsynaptic depolarization is necessary for the induction of
LTP in visual cortex.
Received 13 February 1995; accepted in final form 19 July 1995.
APS Manuscript Number J98-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.