such as "Introduction", "Conclusion"..etc
Department of Anatomy and Neuroscience Training Program, University
of Wisconsin Medical School, Madison, Wisconsin 53706
The Journal of Neurophysiology Vol. 83 No. 5 May 2000, pp. 2626-2638.
Hefti, Brenda J. and
Philip H. Smith.
Anatomy, Physiology, and Synaptic Responses of Rat Layer V
Auditory Cortical Cells and Effects of Intracellular GABAAJ. Neurophysiol. 83: 2626-2638, 2000.
The varied extracortical targets of layer V
make it an important site for cortical processing and output, which may
be regulatedby differences in the pyramidal neurons found there. Two
populationsof projection neurons, regular spiking (RS) and intrinsic
bursting(IB), have been identified in layer V of some sensory
cortices,and differences in their inhibitory inputs have been
indirectlydemonstrated. In this report, IB and RS cells were
identifiedin rat auditory cortical slices, and differences in
thalamocorticalinhibition reaching RS and IB cells were demonstrated
directlyusing intracellular GABAA blockers.
Thalamocortical synaptic inputto RS cells was always a combination of
excitation and both GABAAand GABAB inhibition.
Stimulation seldom triggered a suprathresholdresponse. IB cell
synaptic responses were mostly excitatory, andstimulation usually
triggered action potentials. This apparentdifference was confirmed
directly using intracellular chloridechannel blockers. Before
intracellular diffusion, synaptic responseswere stable and similar to
control conditions. Subsequently, GABAAwas blocked,
revealing a cell's total excitatory input. On GABAAblockade, RS cells responded to synaptic stimulation with large,suprathreshold excitatory events, indicating that excitation,while
always present in these cells, is masked by GABAA. In IBcells that had visible GABAA input, it often masked an
excitatorypostsynaptic potential (EPSP) that could lead to additional
suprathresholdevents. These findings indicate that IB cells receive
less GABAA-mediatedinhibitory input and are able to spike
or burst in response tothalamocortical synaptic stimulation far more
readily than RScells. Such differences may have implications for the
influenceeach cell type exerts on its postsynaptictargets.
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