Instrumentation For, And Application Of, Novel Electrochemical Tools For In Vivo Analysis Of Neurotransmitters In The Context Of Psychiatric Disease

ABSTRACTSerotonin’s involvement in many physiological processes including anxiety, stress, compulsivity, and mood has been speculated for decades. Insufficient progress in our understanding of serotonin chemistry is due to the lack of effective tools to selectively measure this neurotransmitter on a neurotransmission-relevant time scale in vivo. An analytical technique for serotonin measurements, fast-scan cyclic voltammetry (FSCV), was pioneered in the last decade in anesthetized rodents and is beginning to shed light on the complexity of serotonergic activity on a sub-second timescale. Complementary, more recent technological innovations have enabled ambient neurotransmitter levels to be determined every few seconds using a method called fast-scan controlled-adsorption voltammetry (FSCAV). Chapter 1 of this thesis is an introduction to the work. In Chapter 2, the traditional experimental challenges that have thus far limited serotonin measurements are discussed and FSCV is highlighted as a technology that overcomes these difficulties. In Chapter 3, a simplified FSCAV module, which can be easily constructed by non-experts in electronics, is presented. This component is composed of two light-emitting diodes (LEDs). Together, this thesis showcases the design and application of improved electrochemical tools for in vivo analysis of neurotransmitters in the context of psychiatric disorders

Serotonin and dopamine:An updated investigation of neurochemical signals surrounding appetitive and aversive stimuli

Many people believe that dopamine and serotonin are key players in experiencing reward and happiness, but this understanding oversimplifies the complex roles these neuromodulators play in influencing behavior. Our current understanding of dopamine and serotonin signaling remains incomplete, limiting the development of effective treatments for neuropsychiatric disorders such as obsessive-compulsive disorder (OCD), addiction, depression, and Parkinson’s disease. In this thesis, we employed high-precision techniques with high specificity, sensitivity, and temporal resolution to better characterize dopamine and serotonin signaling. By utilizing fast-scan cyclic voltammetry (FSCV) to measure real-time serotonin and dopamine release and optogenetics to selectively activate serotonergic neurons, we investigated how these neuromodulators respond to appetitive and aversive stimuli on behaviorally-relevant timescales. We found dopamine release is differentially regulated across striatal subregions and that, within the ventromedial striatum (VMS), value-based changes in dopamine signaling in response to rewards occur rapidly and incorporate both model-based and model-free reinforcement learning mechanisms. Additionally, we found that VMS dopamine tracks aversive stimulus duration and prediction but not value or prediction error. Lastly, we observed that serotonin mildly promotes voluntary actions and ongoing movement but does not influence instinctive or compulsive behaviors. Together, our findings provide new insights into how dopamine and serotonin influence behavior in response to appetitive and aversive stimuli. These insights offer promising avenues for improving therapeutic strategies for neuropsychiatric disorders

Serotonin and dopamine:An updated investigation of neurochemical signals surrounding appetitive and aversive stimuli

Many people believe that dopamine and serotonin are key players in experiencing reward and happiness, but this understanding oversimplifies the complex roles these neuromodulators play in influencing behavior. Our current understanding of dopamine and serotonin signaling remains incomplete, limiting the development of effective treatments for neuropsychiatric disorders such as obsessive-compulsive disorder (OCD), addiction, depression, and Parkinson’s disease. In this thesis, we employed high-precision techniques with high specificity, sensitivity, and temporal resolution to better characterize dopamine and serotonin signaling. By utilizing fast-scan cyclic voltammetry (FSCV) to measure real-time serotonin and dopamine release and optogenetics to selectively activate serotonergic neurons, we investigated how these neuromodulators respond to appetitive and aversive stimuli on behaviorally-relevant timescales. We found dopamine release is differentially regulated across striatal subregions and that, within the ventromedial striatum (VMS), value-based changes in dopamine signaling in response to rewards occur rapidly and incorporate both model-based and model-free reinforcement learning mechanisms. Additionally, we found that VMS dopamine tracks aversive stimulus duration and prediction but not value or prediction error. Lastly, we observed that serotonin mildly promotes voluntary actions and ongoing movement but does not influence instinctive or compulsive behaviors. Together, our findings provide new insights into how dopamine and serotonin influence behavior in response to appetitive and aversive stimuli. These insights offer promising avenues for improving therapeutic strategies for neuropsychiatric disorders

Neurotransmission Within the Crayfish

Throughout the world, there are multiple species of invasive crayfish emerging. In Europe and parts of Africa, the Procambarus clarkii species is of concern. In this study, fast-scan cyclic voltammetry was utilized to observe and measure neurotransmitters in real time that were present near the pericardial cavity in freely moving Procambarus clarkii crayfish. Crustaceans, including crayfish, utilize an open circulatory system in which their blood and extracellular tissue fluid, or hemolymph, is pumped by the heart. Within the crayfish open circulatory system, various neurotransmitters are released into their hemolymph and brought back to the heart for circulation. Their heart is located near the dorsum and is centrally positioned below the cervical groove, enabling a consistent and easy location for implantation of a carbon-fiber electrode. Fast-scan cyclic voltammetry allows for quick, accurate data that is recorded in real-time, every 100 milliseconds. Using changes of voltage in carbon-fiber electrodes, fastscan voltammetry measures the reaction of oxidation and reduction peaks of neurotransmitters caused by the carbon surface voltage changes. crawling or the meral spread, histamine (HA) was detected and recorded consistently using a histamine-sensitive waveform. Within our study, results show a slight delay in the recording of histamine after a behavior. This could be due to the placement of the recording electrode and a release of histamine taking place a distance from the heart. It is believed that histamine is located in the pyloric region as well as the eyestalk in all crustaceans. Secondly, results show that the release of histamine was dependent on previous displays of aggressiveness and exertion. The display of more forceful behaviors consistently correlated with higher amounts of histamine, with a mean of 258.86 ± 56.75 ÂμM. Natural behaviors, such as crawling, resulted in a lower average of 123.51 ± 19.70 ÂμM. It was also found that a continuous behavior, such as crawling, results in a gradual decrease of histamine levels. Once the crayfish comes upon a challenge or threat and an additional behavior is portrayed, a spike in histamine will result. Lastly, histamine levels proved to steadily drop once the crayfish was left alone after a period of aggressive and defensive behavior. Our hypothesis on the role of histamine is that its inhibitory effects within the gastric mill are indeed shutting down the digestive system to allow the crayfish to move, similar to a fight or flight response. The purpose of this study is to better understand the crayfish general physiology and to assess the role histamine plays in regulating their behavior. Future studies will look to obtain a better understanding of the role of histamine in crayfish behavior by investigating the location of histamine release. By developing a better understanding of crayfish behavior, further investigations of preventative plans can become possible. *This scholar and faculty mentor have requested that only an abstract be published

A simplified LED-driven switch for fast-scan controlled-adsorption voltammetry instrumentation

Fast-scan cyclic voltammetry (FSCV) is an analytical tool used to probe neurochemical processes in real-time. A major drawback for specialized applications of FSCV is that instrumentation must be constructed or modified in-house by those with expertise in electronics. One such specialized application is the newly developed fast-scan controlled-adsorption voltammetry (FSCAV) that measures basal (tonic) in vivo dopamine and serotonin concentrations. FSCAV requires additional software and equipment (an operational amplifier coupled to a transistor-transistor logic) allowing the system to switch between applying a FSCV waveform and a constant potential to the working electrode. Herein we describe a novel, simplified switching component to facilitate the integration of FSCAV into existing FSCV instruments, thereby making this method more accessible to the community. Specifically, we employ two light emitting diodes (LEDs) to generate the voltage needed to drive a NPN bipolar junction transistor, substantially streamlining the circuitry and fabrication of the switching component. We performed in vitro and in vivo analyses to compare the new LED circuit vs. the original switch. Our data shows that the novel simplified switching component performs equally well when compared to traditional instrumentation. Thus, we present a new, simplified scheme to perform FSCAV that is cheap, simple, and easy to construct by individuals without a background in engineering and electronics

Discovery of 2,4-dimethoxypyridines as novel autophagy inhibitors

© 2018 Elsevier Ltd Autophagy is a catabolic process, which mediates degradation of cellular components and has important roles in health and disease. Therefore, small molecule modulators of autophagy are in great demand. Herein, we describe a phenotypic high-content screen for autophagy inhibitors, which led to the discovery of a dimethoxypyridine-based class of autophagy inhibitors, which derive from previously reported, natural product-inspired MAP4K4 inhibitors. Comprehensive structure-activity relationship studies led to a potent compound, and biological validation experiments indicated that the mode of action was upstream or independent of mTOR

Ligand-free copper(I) oxide nanoparticle-catalysed amination of aryl halides in ionic liquids

In the following, we present a simple and feasible methodology for a C-N coupling reaction using nanoscale Cu2O catalysts incorporated in n-Bu4POAc ionic liquid media. It is shown that a wide range of amines and aryl halides can be coupled selectively in high yields, without the use of ligands or additives (bases) and without precautions against water or air. All catalyses can be carried out with a nanoparticle catalyst loading as low as 5 mol%, based on the used precursor

Facile Immobilization of a Lewis Acid Polyoxometalate onto Layered Double Hydroxides for Highly Efficient N-Oxidation of Pyridine-Based Derivatives and Denitrogenation

N-Oxides are a class of highly important compounds which are widely used as synthetic intermediates. In this paper, we demonstrate for the first time the use of a polyoxometalate (POM) based composite material, as highly efficient heterogeneous catalyst for the N-oxidation of pyridines and its derivatives in the presence of H2O2 at room temperature. The composite was prepared by intercalation of the [La(PW11O39)2]11- anion into a tris(hydroxymethyl)aminomethane (Tris) modified layered double hydroxides (LDHs). Additionally, the Tris-LDH-La(PW11)2–based catalyst has been employed for the denitrogenation of a model oil mixture in the presence of [bmim]BF4 and H2O2. Deep denitrogenation can be achieved in 40 minutes at 75 °C. Finally, the heterogeneous catalyst can be easily recovered and reused at least ten times without measurable decrease of the catalytic activity and disintegration of the Tris-LDH-La(PW11)2 structure

Palatal development of preterm and low birthweight infants compared to term infants – What do we know? Part 2: The palate of the preterm/low birthweight infant

BACKGROUND: Well-designed clinical studies on the palatal development in preterm and low birthweight infants are desirable because the literature is characterized by contradictory results. It could be shown that knowledge about 'normal' palatal development is still weak as well (Part 1). The objective of this review is therefore to contribute a fundamental analysis of methodologies, confounding factors, and outcomes of studies on palatal development in preterm and low birthweight infants. METHODS: An electronic literature search as well as hand searches were performed based on Cochrane search strategies including sources of more than a century in English, German, and French. Original data were recalculated from studies which primarily dealt with both preterm and term infants. The extracted data, especially those from non-English paper sources, were provided unfiltered for comparison. RESULTS: Seventy-eight out of 155 included articles were analyzed for palatal morphology of preterm infants. Intubation, feeding tubes, feeding mode, tube characteristics, restriction of oral functions, kind of diet, cranial form and birthweight were seen as causes contributing to altered palatal morphology. Changes associated with intubation concern length, depth, width, asymmetry, crossbite, and contour of the palate. The phenomenon 'grooving' has also been described as a complication associated with oral intubation. However, this phenomenon suffers from lack of a clear-cut definition. Head flattening, pressure from the oral tube, pathologic or impaired tongue function, and broadening of the alveolar ridges adjacent to the tube have been raised as causes of 'grooving'. Metrically, the palates of intubated preterm infants remain narrower, which has been examined up to the age of the late mixed dentition. CONCLUSION: There is no evidence that would justify the exclusion of any of the raised causes contributing to palatal alteration. Thus, early orthodontic and logopedic control of formerly orally intubated preterm infants is recommended, as opposed to non-intubated infants. From the orthodontic point of view, nasal intubation should be favored. The role that palatal protection plates and pressure-dispersing pads for the head have in palatal development remains unclear