[Abstract Title]. - Society for Neuroscience

Abstract: We determined the peak excitatory conductance necessary to reach threshold for
action potential (AP) generation in CA1 pyramidal cells (PCs) recorded in acute hippocampal
slices obtained from 3-4 weeks old rats. PCs were initially recorded in the loose patch
configuration and Schaffer collaterals stimulated at an intensity just sufficient to reach threshold
for AP generation. We subsequently gained whole cell access to the neurons and determined the
peak conductance of the underlying "threshold" excitatory postsynaptic current (EPSG) by
holding the PC at the reversal potential for inhibition. We found that the threshold EPSG varied
over a wide range, between 3 and 30 nS. The threshold EPSG correlated with the number of
stimulated Schaffer collaterals. Both the variability in the threshold EPSG and the correlation
with the number of activated Schaffer collaterals were abolished in the presence of the GABA A
receptor antagonists gabazine. We determined the peak conductance of feed forward inhibitory
postsynaptic currents (IPSGs) elicited in response to stimulation of Schaffer collaterals at
threshold for AP generation and found that it strongly correlated with the evoked threshold
EPSG.
These data suggest that the threshold excitation in PCs is not fixed but varies as a function of
input strength. This variability depends on the presence of feed-forward inhibition. By
instantaneously adjusting pyramidal cell excitability to the strength of incoming activity, feedforward
inhibitory circuits allow the pyramidal cell population to be sensitive to weak stimuli yet
not to saturate with stronger ones. This results in an expansion of the dynamic range of the CA1
region to incoming activity.
Disclosures: A. Marin-Burgin , None; F.R. Pouille, None; M. Scanziani, None.
Poster
237. Synaptic Integration II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 237.5/D30
Topic: B.07.c. Synaptic integration
Support: Ribble Undergraduate Scholarship, University of Kentucky, Department of Biology
Title: Comparison of the autonomic response of multiple sensory modalities in crayfish
Authors: *M. M. ROBINSON, T. SPENCE, T. MCLAURINE, S. M. BIERBOWER, R. L.
COOPER;
Univ. Kentucky, Lexington, KY
Abstract: Most organisms show diversity in the type and amount of peripheral sensors which
allow for detection of different sensory stimuli within and across multiple sensory modalities.