Accurate and high throughput methods of measuring animal behavior are critical for many branches of neuroscience, allowing for mechanistic studies and preclinical drug testing. Methodological limitations contribute to narrow investigations, which may overlook the interplay between distinct but related behaviors, like affective behaviors and executive function (EF). To prevent such oversight, researchers can perform test batteries, or multiple assessments in one study. However, test batteries often exclude cognitive behaviors due to their lengthy testing period. This dissertation first reviews current evidence related to the investigation and relation of affective, pain-like, and operant behaviors in rodent models. Then, I demonstrate the use of traditional and novel test batteries to investigate these behavioral changes in multiple mouse models.
First, I investigated affective and pain-like behavior in mice lacking Nape-pld, a key enzyme that synthesizes lipid mediators which activate receptors in the endocannabinoid system. I found that these mice displayed reduced sucrose preference, but otherwise normal anxiety- and depression-like behavior, and had baseline differences in thermal nociception and inflammation response. Then, I investigated the affective, pain-like, and operant effects of chronic vapor exposure (CVE) to vehicle or nicotine (NIC). Regardless of NIC content, acute abstinence from CVE increased mechanical sensitivity and self-grooming, while chronic abstinence from NIC CVE resulted in motor stimulation. Other traditional anxiety- and depression-like behaviors were unchanged by CVE. In an operant test battery, acute abstinence from NIC CVE impaired acquisition, decreased sucrose motivation, and impaired the response to aversive rewards. Finally, I developed a protocol for the high throughput analysis of six operant tests which can be completed in as few as nineteen sessions, significantly fewer sessions than traditional operant tests. This battery investigates multiple aspects of goal-directed behavior and EF including operant acquisition, cognitive flexibility, reward devaluation, motivation via response to increased instrumental effort, cue devaluation or the extinction of learned behavior, and reacquisition. I validated several of these tests by demonstrating that lesions to specific subregions of the orbitofrontal cortex impaired cognitive flexibility and altered response to instrumental effort as observed in traditional operant tests. I then used this battery to investigate the effects of the P129T mutation, which results in a mutated version of the Fatty Acid Amide Hydrolase (FAAH) enzyme that is associated with addiction, in male and female mice. Knock-in animals displayed reduced activity in response to increasing instrumental effort, and reduced activity on the first day of an extinction test. Then, to encourage others to use this new operant battery I outlined how to efficiently collect data, shared a database for customizable analysis, and described common issues and how to solve them. This protocol has potential implications for many aspects of neuroscience including the investigation of novel therapeutics and the neural circuitry underlying behaviors.
Together, the information in this dissertation demonstrates the utility of multi-faceted behavioral assays and the combination of traditional and novel approaches to collect more comprehensive behavioral data, which will allow researchers to better investigate neural circuitry underlying behaviors or the behavioral changes associated with novel therapeutics. / Doctor of Philosophy / By measuring animal behavior researchers can gain insight into how specific brain regions interact to influence choice and action. Limitations in testing methods mean that researchers may fail to investigate the relationship between distinct aspects of behavior, like the influence of emotional state or pain on cognition. To prevent such oversight researchers can perform a test battery, a specific series of multiple tests that measures several different aspects of behavior. Traditional test batteries often overlook cognitive or operant (learning to perform an action for reward) behaviors due to time constraints, which limits their translational potential. This dissertation provides a brief overview of the ways that researchers investigate affective (emotional), pain-like (physical discomfort), and goal-directed behaviors. It further has a broad focus on mouse models related to addiction or the endocannabinoid system (ECS), which is shown to play a role in mood, pain (e.g., perception, relief, and inflammation), and cognition. Using a traditional test battery, we demonstrate that mice lacking a key enzyme in the ECS have altered responses to sugar, heat, and inflammation, but display otherwise normal performance in anxiety-, depression-, and pain-like tests. Next, we used a combined traditional and operant battery to investigate the effects of chronic vapor exposure (CVE) and nicotine in mice. We found that regardless of nicotine content, acute abstinence from CVE increased physical sensitivity and self-grooming but spared other anxiety- and depression-like behaviors. Acute abstinence from nicotine CVE resulted in motor stimulation, impaired operant learning, lower motivation for sucrose reward, and an impaired ability to withhold responding when presented with a bitter reward. Finally, I outline a novel operant test battery that addresses the limitations of current operant chamber- or place-based batteries. Using this battery, I first demonstrate that it captures similar behavioral changes to those seen in traditional operant chambers. Then, I demonstrate that mice containing an ECS mutation associated with problem drug use in humans display less motivation for food reward in response to increased effort, and more quickly inhibit a learned behavior when reward delivery is interrupted. I also found that in response to increased effort for reward or bitter rewards, male mice are more likely to alter their behavioral strategy. To encourage others to use this new operant battery I outlined how to efficiently collect data, shared a database for customizable analysis, and described common issues and how to solve them. This protocol has the potential to improve upon traditional tasks while opening cognitive research to more scientists. This has implications for many fields of neuroscience, especially the investigation of novel therapeutics and investigation of the neural circuitry underlying various disorders.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/117372 |
| Date | 16 January 2024 |
| Creators | Murdaugh, Laura Bethany |
| Contributors | Graduate School, Buczynski, Matthew, Vijayan, Sujith, Campbell, Susan, Theus, Michelle Hedrick |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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