Graduation Semester and Year

2018

Language

English

Document Type

Thesis

Degree Name

Master of Science in Psychology

Department

Psychology

First Advisor

Yuan Bo Peng

Abstract

Post herpetic neuralgia (PHN) is experienced as burning pain in the facial region, caused by nerve damage from the herpes zoster virus. The pain often becomes chronic and debilitating. Investigations into the pain pathway become vital. Pain itself is multidimensional, consisting of both the sensory and affective experiences. One of the primary brain substrates for transmitting sensory signals in the facial muscles is through ventral posterior medial thalamus (VPM). Anterior cingulate cortex (ACC) has been shown to be vital in the affective experience of pain, so investigating both of these areas in freely behaving animals can provide important information. Local field potential (LFP) recordings measure changes to the summation of subthreshold neuronal activity. A new investigational method of using a designer receptor activated by a designer drug (DREADD) (Armbruster et al, 2007) has been shown by our lab to inhibit both neuronal activity in the VPM and spontaneous pain behavior in a formalin pain model in rats. By application of this DREADD, a modified G Protein Coupled Receptor (mGPCR), the LFPs of both VPM and ACC were recorded simultaneously to see how the inhibition of neuronal activity in the VPM affects neuronal activity in the ACC in freely behaving rats in a more clinically relevant pain model, PHN. Additionally, a place escape-avoidance paradigm was used to measure affective experience of pain (Fuchs et al, 2014). mGPCR was infused into the VPM of Sprague Dawley rats and LFP recording electrodes were implanted into the VPM and ACC. A week later, the whisker pads were injected with either varicella zoster virus (VZV) infected cells or MeWo (control) uninfected cells. Within 7 days, the LFP for both VPM and ACC were recorded, mGPCR was activated via IP injection (or saline for control) of clozapine N oxide. A new baseline was recorded and the animals were tested using a preferred escape-avoidance paradigm. We found that, similar to the spontaneous pain behavior, escape-avoidance behavior is significantly reduced in the drug group compared to the no drug group. Changes in LFP activity of delta, theta, and alpha wavelengths were noted with increased activity observed in PHN rats compared to control and also between the drug and no drug group in PHN. Overall thalamocortical coherence between VPM and ACC also increased over time. Understanding how manipulation of thalamic activity can affect changes in both neuronal activity and pain behavior can bring us closer to identifying novel ways to relieve post herpetic neuralgia in humans.

Keywords

DREADD, mGPCR, Post herpetic neuralgia, Orofacial pain, ACC, VPM

Disciplines

Psychology | Social and Behavioral Sciences

Comments

Degree granted by The University of Texas at Arlington

Included in

Psychology Commons

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