DIFFERENTIAL IMPACT OF MINIATURE SYNAPTIC POTENTIALS
ON THE SOMA AND DENDRITES OF PYRAMIDAL NEURONS IN VIVO
Denis Parˇ, Elen LeBel and Eric J. Lang
Dˇpartement de Physiologie, Facultˇ de Mˇdecine,
Universitˇ Laval, Quˇbec, (QUE), CANADA, G1K 7P4
Department of Physiology and Neuroscience, New York University Medical Center,
550 First Avenue, New York, NY 10016, USA
APStracts 4:0084N, 1997.
ABSTRACT
We studied the impact of transmitter release resistant to tetrodotoxin (TTX)
in morphologically-identified neocortical pyramidal neurons recorded
intracellularly in barbiturate-anesthetized cats. It was observed that TTX-
resistant release occurs in pyramidal neurons in vivo and at much higher
frequencies than was previously reported in vitro. Further, in agreement with
previous findings indicating that GABAergic and glutamatergic synapses are
differentially distributed in the soma and dendrites of pyramidal cells, we
found that most minis were sensitive to GABAA or AMPA antagonists in presumed
somatic and dendritic impalements, respectively. Pharamacological blockage of
spontaneous synaptic events produced large increases in input resistance that
were more important in dendritic (»50%) than somatic (»10%) impalements. These
findings imply that, in the intact brain, pyramidal neurons are submitted to
an intense spike-independent synaptic bombardment that decreases the space
constant of the cells. These results should be taken into account when
extrapolating in vitro findings to intact brains.
Received 14 April 1997; accepted in final form 11 June 1997.
APS Manuscript Number J299-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 15 July 1997