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Date Permissions Signed

4-15-2020

Date of Award

Spring 2020

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Rose, Jacqueline

Second Advisor

Singh-Cundy, Anu

Third Advisor

Dahlberg, Lina

Fourth Advisor

Serrano-Moreno, José Ramón

Abstract

Retrograde signaling from downstream effectors (i.e., motor neurons) can modulate plasticity. Much research has focused on the learned association of closely timed sensory stimuli. By comparison, there is less research probing the potential influence of how or if activation at downstream neuromuscular junctions (NMJ) could modulate associative conditioning. Using channelrhodopsin activation of body wall muscle and different motor neuron subsets (cholinergic motor neurons that drive contraction and GABAergic motor neurons that drive relaxation of muscle) in the Caenorhabditis elegans (C. elegans) model system, we examined if concurrent excitation in these downstream circuits influences associative conditioning.

Conditioning consisted of pairing two distinct sensory stimuli, mechanosensory (vibration) and blue light (~480nm). Each stimulus drives a locomotor response on its own and we have shown that pairing delivery of these two stimuli alters the subsequent locomotor response to vibration. Animals that expressed channelrhodopsin in the body wall muscle (pmyo-3::ChR2), excitatory motor neurons (punc-17::ChR2) or the inhibitory motor neurons (punc-47::ChR2) received associative vibration-light conditioning. Thus, the blue light stimulus simultaneously functioned as both associating sensory stimulus and activator of channelrhodopsin, when the necessary cofactor was present, all-trans-retinol (ATR+).

Results showed wild type C. elegans typically pause for a longer duration following associative vibration-light conditioning. Following vibration-light conditioning, pmyo-3::ChR2 exhibited a complete disruption of learning. While trained ATR+ punc-17::ChR2 and punc-47::ChR2 animals showed partially disrupted conditioned locomotor behavior, as compared to controls. Together, this data suggests that co-activation of the downstream body wall muscle and motorneurons interferes with upstream associative conditioning.

Type

Text

Keywords

Acetylcholine, Associative Conditioning, Body Wall Muscle, GABA, Learning, Neuromuscular Junction

Publisher

Western Washington University

OCLC Number

1154631609

Subject – LCSH

Caenorhabditis elegans--Nervous system; Neuromuscular transmission; Motor neurons; Conditioned response; Optogenetics

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Rights Statement

http://rightsstatements.org/vocab/InC-EDU/1.0/

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