The Journal of Neuroscience, July 1, 1999, 19(13):5528-5548
Arginine Analogs Modify Signal Detection by Neurons in the
Visual Cortex
Prakash
Kara and
Michael J.
Friedlander
Department of Physiology & Biophysics and Department of
Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama
35294
Nitric oxide (NO) modulates neurotransmitter release, induction of
long-term synaptic potentiation and depression, and activity levels of
neurons. However, it is not known whether NO contributes to the ability
of the CNS to distinguish sensory signals from background noise
and/or extract sensory information with greater reliability. We
addressed these questions in the visual cortex, in vivo,
using electrophysiological recording and analysis of signal detection
from individual neurons. This was combined with microiontophoretic
application of arginine analogs that either upregulate or downregulate
the brain's endogenous NO-generating pathways or compounds that
produce exogenous NO. Protocols that enhance NO levels generally
increased the number of action potentials per trial evoked by visual
stimuli, improved signal detection, and decreased the coefficient of
variation of visually evoked responses, whereas NO-reducing protocols
predominantly had complementary effects. Control experiments
demonstrate that these effects are likely attributable to the specific
ability of these arginine compounds to modify NO levels versus other
nonspecific effects. Differential effects between neighboring cells and
between single-cell receptive subfields suggest that these actions have
a significant direct neural component versus exclusively operating
indirectly on neurons through the central vascular actions of NO.
Key words:
nitric oxide; visual cortex; signal detection; arginine; nitric oxide synthase; striate cortex; information processing; signal-to-noise
Copyright © 1999 Society for Neuroscience 0270-6474/99/19135528-21$05.00/0