The Journal of Neuroscience, July 15, 1999, 19(14):5721-5730
Three GABA Receptor-Mediated Postsynaptic Potentials in
Interneurons in the Rat Lateral Geniculate Nucleus
J. Julius
Zhu1, 2 and
Fu-Sun
Lo1
1 Shanghai Brain Research Institute and Institute of
Neuroscience, Chinese Academy of Sciences, Shanghai 200031, China, and
2 Abteilung Zellphysiologie, Max-Planck-Institut für
medizinische Forschung, Heidelberg D-69120, Germany
Inhibition is crucial for the thalamus to relay sensory information
from the periphery to the cortex and to participate in thalamocortical
oscillations. However, the properties of inhibitory synaptic events in
interneurons are poorly defined because in part of the technical
difficulty of obtaining stable recording from these small cells. With
the whole-cell recording technique, we obtained stable recordings from
local interneurons in the lateral geniculate nucleus and studied their
inhibitory synaptic properties. We found that interneurons expressed
three different types of GABA receptors: bicuculline-sensitive
GABAA receptors, bicuculline-insensitive GABAA
receptors, and GABAB receptors. The reversal potentials of
GABA responses were estimated by polarizing the membrane potential. The
GABAA receptor-mediated responses had a reversal potential of approximately 
82 mV, consistent with mediation via
Cl
channels. The reversal potential for the
GABAB response was 97 mV, consistent with it being a
K+ conductance. The roles of these GABA receptors in
postsynaptic responses were also examined in interneurons. Optic tract
stimulation evoked a disynaptic IPSP that was mediated by all
three types of GABA receptors and depended on activation of geniculate
interneurons. Stimulation of the thalamic reticular nucleus evoked an
IPSP, which appeared to be mediated exclusively by
bicuculline-sensitive GABAA receptors and depended on the
activation of reticular cells. The results indicate that geniculate
interneurons form a complex neuronal circuitry with thalamocortical and
reticular cells via feed-forward and feedback circuits, suggesting that
they play a more important role in thalamic function than thought previously.
Key words:
dendrite; cortex; visual cortex; thalamus; thalamic
reticular nucleus; lateral posterior nucleus; superior colliculus; inhibitory circuits; oscillation; epilepsy; GABAC receptor; retina
Copyright © 1999 Society for Neuroscience 0270-6474/99/19145721-10$05.00/0
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