Journal of Neuroscience, Vol 4, 1607-1617, Copyright © 1984 by Society for Neuroscience
The effect of norepinephrine on visual cortical neurons in kittens and adult cats
TO Videen, NW Daw and RK Rader
The responses of visual cortical neurons during iontophoresis of
norepinephrine (NE) were compared in kittens and adult cats. One type of
neuronal "plasticity" (the ability of visual cortical neurons to have their
response properties markedly altered during exposure to a restricted visual
environment) normally occurs only in young kittens and has been
hypothesized to depend on the presence of NE. We investigated this
hypothesis in terms of a model of synaptic plasticity which suggested that
NE would selectively enhance the evoked responses of neurons and that this
enhancement might exist to a greater extent in kittens than in adult cats.
The responses of 72% (43 of 60) of all neurons sampled decreased during NE
iontophoresis, while the responses of only a few neurons (3 of 60)
increased. Reduced activity occurred in roughly equal percentages of simple
and complex cells. We also looked for differences in NE modulation of the
"signal-to-noise" ratio of neurons. Most neurons had little spontaneous
activity, but, of those that did, the signal-to-noise ratio increased in
some instances and decreased in others. No difference in any of the effects
of NE was observed between kittens and adult cats. The role of NE in
cortical plasticity is discussed.
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