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Passive spatial and temporal integration of excitatory synaptic inputs in cerebellar Purkinje cells of young rats.
Heck D, Borst A, Antkowiak B.
and Biophysics, Institute of Biology III, Albert-Ludwigs University of
Freiburg, Schanzlestrasse 1, 79104 Freiburg, Germany.
We have investigated the
integration of excitatory (parallel fiber) synaptic inputs in
cerebellar Purkinje cells of young rats in vitro and in a compartmental
model of such a cell, based on 3D morphological reconstruction.
Excitatory synaptic inputs at two independent dendritic sites were
activated by electrical stimulation with various delays between the two
stimuli. Population postsynaptic potentials summed linearly under
current clamp condition when the two dendritic input sites were
spatially separated (>200 microm) but sublinearly, in a delay
dependent manner, when the input sites were close (<50 microm) to
each other. Population postsynaptic currents measured under voltage
clamp conditions summed linearly independent of the spatial and
temporal separation of inputs. Summation of inputs in a passive
compartmental model of a Purkinje cell was similar to that of Purkinje
cells in vitro. We show that sublinear summation of neighboring inputs
is independent of inhibitory mechanisms and suggest that sublinearity
is mainly due to a locally reduced driving force.
PMID: 12676348 [PubMed - indexed for MEDLINE]