GABAergic synaptic transmission triggers action potentials in thalamic reticular nucleus neurons.
GABAergic neurons in the thalamic reticular nucleus (TRN) form powerful inhibitory connections with several dorsal thalamic nuclei, thereby controlling attention, sensory processing, and synchronous oscillations in the thalamocortical system. TRN neurons are interconnected by a network of GABAergic synapses, but their properties and their role in shaping TRN neuronal activity are not well understood. Using recording techniques aimed to minimize changes in the intracellular milieu, we show that synaptic GABA(A) receptor activation triggers postsynaptic depolarizations in mouse TRN neurons. Immunohistochemical data indicate that TRN neurons express very low levels of the Cl(-) transporter KCC2. In agreement, perforated-patch recordings show that intracellular Cl(-) levels are high in TRN neurons, resulting in a Cl(-) reversal potential (E(Cl)) significantly depolarized from rest. Additionally, we find that GABA(A) receptor-evoked depolarizations are amplified by the activation of postsynaptic T-type Ca(2+) channels, leading to dendritic Ca(2+) increases and the generation of burst firing in TRN neurons. In turn, GABA-evoked burst firing results in delayed and long-lasting feedforward inhibition in thalamic relay cells. Our results show that GABA-evoked depolarizations can interact with T-type Ca(2+) channels to powerfully control spike generation in TRN neurons.
Department of Neurobiology and Anatomy, University of Texas Medical School, Houston, Texas 77030, USA.
Yan-Gang
YG
Sun
Chia-Shan
CS
Wu
John J
JJ
Renger
Victor N
VN
Uebele
Hui-Chen
HC
Lu
Michael
M
Beierlein
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D020747:Calcium Channels, T-Type / Q000502:physiology; D005260:Female; D018756:GABA Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D018080:Receptors, GABA-B / Q000187:drug effects / Q000502:physiology; D027981:Symporters / Q000235:genetics / Q000502:physiology; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013787:Thalamic Nuclei / Q000166:cytology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*; D000096922:K Cl- Cotransporters
D020747:Calcium Channels, T-Type; D018756:GABA Antagonists; D018080:Receptors, GABA-B; D027981:Symporters; D005680:gamma-Aminobutyric Acid; D000096922:K Cl- Cotransporters