Neuromodulation of Inhibitory Activity in Thalamocortical Circuits

140 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.In last chapter, I demonstrate that the inhibitory currents arising from interneurons and TRN neurons can be distinguished by their kinetics. The local interneurons are of interest because these neurons have two distinct outputs: axonal and dendritic. These cells have classical axonal outputs, termed F1 terminals, as well as presynaptic dendrites that also release GABA and have been termed F2 terminals. In contrast, TRN neurons give rise to only axonal, F1 outputs. My data indicate that the rise time, slope and half-width of miniature ISPCs (mIPSCs) recorded in dLGN relay neurons have greater variance than those recorded in ventrobasal nucleus (VB) neurons. It is important to note that in rodents, the dLGN has local interneurons (F1 & F2 inputs) whereas VB does not contain interneurons and thus lack F2 innervation. Paired recordings from synaptically-coupled interneurons and dLGN relay cells were used to characterize the IPSCs of this connection. The rise time and half-width of these unitary IPSCs were similar to mIPSCs in dLGN relay neurons and were significantly larger than mIPSCs in VB relay neurons. In order to differentiate F1 outputs from F2 output, we next subdivided relay neurons based upon their response to mGluR activation. In ACPD-positive neurons (F2 + F1 activity) mIPSCs have larger rise times and half-widths compared to those in ACPD-negative neurons (F1 only) as well as VB neurons. These results suggest that dendritic output might provide functionally distinct inhibitory current that differ from axon-originated inhibition, and thereby may play distinct role in modulating the visual information processing. (Abstract shortened by UMI.).U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD