Date of Award

Winter 2020

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Arturo Andrade

Second Advisor

Xuanmao Chen

Third Advisor

Robert Mair

Abstract

The thalamic reticular nucleus (TRN) filters somatosensory stimuli by providing inhibition to the excitatory thalamic relay nuclei, which then communicate with the cortex to appropriately integrate and respond to sensory stimuli. The TRN is also responsible for generating and maintaining sleep spindles, which are important for memory and cognition, and are disrupted in various psychiatric disorders. Previous studies have shown that the TRN is comprised of several neuronal subpopulations that carry out specific functions. These neurons can be distinguished using peptide markers such as parvalbumin (PV), somatostatin (SST), and calbindin (CB). In this thesis, I identified a novel neuronal population in the TRN that expresses the peptide cholecystokinin (CCK) and distal-less homeobox gene 5/6 (Dlx5/6). CCK;Dlx5/6 neurons have been widely studied in the hippocampus and amygdala where they have been shown to highly express the type 1 cannabinoid receptor (CB1R) and produce a long-lasting inhibition of pyramidal neurons. However, basic characterization of CCK;Dlx5/6 neurons has been missing. Through immunohistochemical assays, we found that CCK;Dlx5/6 neurons of the TRN express CB1R and the CCK peptide. Our results show that CCK;Dlx5/6 are highly concentrated in the dorsal areas of the TRN relative to the ventral ones, dorsal areas of the TRN are associated with processing of visual cues. Our preliminary results also show that dorsal and ventromedial areas of the thalamus receive more inputs from CCK;Dlx5/6 neurons than ventral and medial thalamic areas. Furthermore, some of the CCK;Dlx5/6 neurons establish perisomatic synapses with neurons of the lateral dorsal nucleus of the thalamus, this type of connectivity is consistent with previous observations for CCK neurons in amygdala and hippocampus. Taken together our results provide insights into the anatomy of CCK;Dlx5/6 neurons that suggest a potential role of these neurons in visual processing.

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