Intrinsic modulators of auditory thalamocortical transmission.
Neurons in layer 4 of the primary auditory cortex receive convergent glutamatergic inputs from thalamic and cortical projections that activate different groups of postsynaptic glutamate receptors. Of particular interest in layer 4 neurons are the Group II metabotropic glutamate receptors (mGluRs), which hyperpolarize neurons postsynaptically via the downstream opening of GIRK channels. This pronounced effect on membrane conductance could influence the neuronal processing of synaptic inputs, such as those from the thalamus, essentially modulating information flow through the thalamocortical pathway. To examine how Group II mGluRs affect thalamocortical transmission, we used an in vitro slice preparation of the auditory thalamocortical pathways in the mouse to examine synaptic transmission under conditions where Group II mGluRs were activated. We found that both pre- and post-synaptic Group II mGluRs are involved in the attenuation of thalamocortical EPSP/Cs. Thus, thalamocortical synaptic transmission is suppressed via the presynaptic reduction of thalamocortical neurotransmitter release and the postsynaptic inhibition of the layer 4 thalamorecipient neurons. This could enable the thalamocortical pathway to autoregulate transmission, via either a gating or gain control mechanism, or both.
Department of Comparative Biomedical Sciences, Louisiana State University, School of Veterinary Medicine, Baton Rouge, LA 70803, USA. cclee@lsu.edu
Charles C
CC
Lee
S Murray
SM
Sherman
D000818:Animals; D001303:Auditory Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001306:Auditory Pathways / Q000378:metabolism; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000737:chemistry / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D006706:Homeostasis; D066298:In Vitro Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010477:Perfusion; D010782:Photolysis; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000378:metabolism*; D013003:Somatosensory Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects; D013788:Thalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D018690:Excitatory Amino Acid Agonists; D018094:Receptors, Metabotropic Glutamate