# Formation and Maturation of Projections Between Thalamic Reticular Nucleus and Dorsal Lateral Geniculate Nucleus

> **NIH NIH F30** · UNIVERSITY OF LOUISVILLE · 2020 · $50,520

## Abstract

Project Summary
One of the preeminent models used to study the development of thalamic circuitry is the mouse visual
thalamus. Most studies on this system have focused on the retinogeniculate pathway that connects retinal
axons with relay neurons of the dorsal lateral geniculate nucleus (dLGN). These relay neurons transmit visual
information to the visual cortex via their axonal projection to primary visual cortex but this projection also sends
axon collaterals to the thalamic reticular nucleus (TRN). The TRN is a GABAergic nucleus that projects to the
dorsal thalamus, including dLGN, and is the main inhibitory projection to these brain regions. Thus, there is a
feedback loop between dLGN and TRN, which is known to mediate visual attention, select thalamocortical
rhythms, and is involved in multiple diseases processes. However, when this loop is formed and how it
develops is currently not known. Furthermore, it is unknown whether the development of these projections are
regulated, like other nonretinal projections to dLGN, by retinal signaling. These questions will be addressed in
three specific aims: Aim 1 will determine when TRN terminals arrive in dLGN, when synapses onto relay
neurons become functional, and how both terminal expanse and synaptic responses mature; Aim 2 will
investigate similar parameters for the innervation of TRN by dLGN, determining when terminals arrive, when
synapses are made and how synaptic responses change over early development; Aim 3 will compare the
developmental time course of these projections TRN and dLGN in the presence and absence of retinal input to
central visual structures in order to determine if retinal terminals coordinate the developmental timing of
innervation. These experiments will utilize transgenic mice that specifically label either the projections from
TRN or those from dLGN. Specifically, the GAD65 mouse will be used to visualize TRN innervation of dLGN
with EGFP while the somatostatin-cre mouse will be crossed to a channelrhodopsin-2 mouse in order to
photoactivate TRN terminals in electrophysiological recordings (aim 1). The corticotropin releasing hormone
cre-recombinase mouse will be used to both stimulate and visualize dLGN inputs to TRN with crosses to either
the channelrhodopsin-2 mouse or an Ai9 reporter line that will label this projection with TdTomato (aim 2).
Finally, these experiments will be repeated after crossing all these mice into a math 5 null background to
genetically remove retinal inputs (aim 3). Together, these experiments will determine how an important
component of the visual system develops and they will test the hypothesis that retinal terminals in dLGN
coordinate the innervation of non-retinal projections to dLGN as well as the axonal projections of dLGN relay
neurons. These studies will not only advance the current understanding of the visual system but will have
implications for circuit development in the thalamus as a whole.

## Key facts

- **NIH application ID:** 9878864
- **Project number:** 5F30EY026792-04
- **Recipient organization:** UNIVERSITY OF LOUISVILLE
- **Principal Investigator:** Peter W Campbell
- **Activity code:** F30 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $50,520
- **Award type:** 5
- **Project period:** 2017-03-01 → 2021-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9878864

## Citation

> US National Institutes of Health, RePORTER application 9878864, Formation and Maturation of Projections Between Thalamic Reticular Nucleus and Dorsal Lateral Geniculate Nucleus (5F30EY026792-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9878864. Licensed CC0.

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