College

Buchtel College of Arts and Sciences

Date of Last Revision

2024-09-19 12:09:10

Major

Biomedical Science

Honors Course

71335

Number of Credits

3

Degree Name

Bachelor of Science

Date of Expected Graduation

Spring 2024

Abstract

Neurons transmit signals through an electrochemical reaction: synapses on dendrites and the cell body receive neurotransmitters, and their effect on the cell determines the signal the cell will transmit. From dendrites to axon and then to another cell at a synaptic cleft, signals can propagate, enhance each other, or inhibit other transmissions until the message is received by the target area. Understanding the science behind neural signaling and structural function begins at the level of the synapse. The neurotransmitter acetylcholine (ACh) plays a substantial role in modulating neural activity in the auditory system, but for many brainstem nuclei the source of cholinergic input is unknown. Identifying the source of ACh holds such significance because different sources are likely to perform different functions. The present study categorizes cholinergic input to the Ventral Nucleus of the Lateral Lemniscus (VNLL), one of the largest sources of inhibitory input to the Inferior Colliculus (IC), a midbrain center that processes nearly all auditory information received by the brain. Using retrograde and anterograde labeling of cholinergic cell bodies and axons, we identified three regions- the Pontomesenphalic Tegmentum (PMT), the Superior Olivary Complex (SOC), and the Lateral Paragigantocellular Nucleus (LPGi)- transmitting acetylcholine to the VNLL in mouse. Mouse models allowed for selective manipulation of cholinergic axons through viral injection of fluorescent protein in transgenic-bred mouse lines. Retrograde experiments identified cholinergic cell bodies in the three regions of interest communicating with the VNLL by labeling cells with a RetroBead marker originally injected into the VNLL followed by antibody tissue staining, and anterograde studies validated this communication pattern by labeling cholinergic axons in the VNLL coming from fluorescent injections placed in each of the three regions of interest. Axon termination patterns demonstrate the degree of communication between these areas and also suggest that individual VNLL neurons receive converging input from multiple cholinergic sources, likely to be active for different roles in modulating VNLL neurons and their responses to sound.

Research Sponsor

Dr. Brian Bagatto

First Reader

Dr. Brett Schofield

Second Reader

Dr. Quin Liu

Honors Faculty Advisor

Dr. Brian Bagatto

Proprietary and/or Confidential Information

No

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