Author:
BIEDA MARK C.,COPENHAGEN DAVID R.
Abstract
Ganglion cells responding only transiently to changes
in illumination are found in many different vertebrate
retinas. The interactions underlying formation of these
transient responses are still poorly understood. Two recently
proposed hypotheses are (1) functional inhibitory pathways
are necessary for transient response production, and (2)
direct inhibition of the ganglion cell has little effect
on its output. Here, we examine these conclusions by using
cell-attached patch-clamp recordings of spiking, whole-cell
recordings of synaptic currents, and computer modeling.
We found that picrotoxin (a GABAA and GABAC
receptor antagonist), bicuculline (a GABAA receptor
antagonist), and strychnine (a glycine receptor antagonist),
applied either singly or in combination, always failed
to convert transient responses to sustained responses.
Application of the GABAB antagonist CGP35348
in the presence of picrotoxin and strychnine also failed
to convert transient responses into sustained responses.
Whole-cell recordings of synaptic currents at various holding
potentials indicated that direct inhibitory inputs to ganglion
cells limit the duration of net excitation, implying that
direct inhibition does act to truncate the ganglion cell
spiking response. Computer simulations using spiking and
synaptic data from combined cell-attached and whole-cell
recordings supported this interpretation. We conclude that
inhibitory pathways are not required for generation of
transient responses, but these pathways do serve to modulate
transient ganglion cell spiking responses. We find that
this modulation occurs, in part, via inhibitory
inputs directly to the ganglion cell.
Publisher
Cambridge University Press (CUP)
Subject
Sensory Systems,Physiology
Cited by
17 articles.
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