Browsing by Subject "Dopamine"
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Item A MULTI-GROUP CONFIRMATORY FACTOR ANALYSIS OF THE REACTIVE- PROACTIVE AGGRESSION QUESTIONNAIRE IN A SAMPLE OF YOUNG ADULTS(2016-11-17) Cooke, Eric Meyers; Armstrong, Todd; Boisvert, Danielle; Zhang, YanAggression has long-term negative effects on humanity as a whole. Because of this, aggression has become an important topic of study across many disciplines. Originally conceptualized as being either non-impulsive or impulsive, aggression has become dichotomized as being reactive or proactive. Each form of aggression has been linked to a variety of genetic, psychological, physiological, and neurobiological correlates. Because research continues to grow in these fields surrounding proactive and reactive aggression, it is important to make sure that measurement tools are assessing aggression appropriately across a variety of groups. One such tool that has emerged recently is the Reactive-Proactive Aggression Questionnaire (RPQ; Raine et al., 2006). Though a number of studies exist testing the validity of the RPQ in adolescent and child populations. No such studies exist examining the factor structure and measurement invariance of proactive and reactive aggression in young adult male and females from different ethnicities. The current study assesses factor structure and measurement invariance in multiple groups of young North American adults. Results show that a two- factor, proactive-reactive, structure fits the current data overall. However, measurement invariance is not achieved across the majority of these groups. Meaning that interpretation of reactive and proactive scores is not the same across gender and ethnicity. Limitations and future directions are discussed.Item Affective responses in cocaine-experienced rats reveal cue-induced drug craving and cocaine reward magnitude(2011-08) Maier, Esther Yvonne; Duvauchelle, Christine L.; Schallert, Timothy; Gonzales, Rueben A.; Gore, Andrea C.; Monfils, Marie H.The development and persistence of cocaine dependence are greatly influenced by emotional affect and cocaine associative learning. Cocaine is known to enhance nucleus accumbens (NAcc) dopamine, serve as a positive reinforcer and produce negative effects, such as anxiety that may influence cocaine intake behavior. In the first study, I investigated the effects of the anxiolytic, diazepam on NAcc dopamine levels and cocaine self-administration behavior. These are two factors associated with cocaine rewarding effects. Diazepam has no effect on NAcc dopamine, but affects cocaine self-administration. This supports the notion that decreasing the anxiogenic effects of cocaine increases the rewarding value in a dopamine independent manner. Therefore, increasing the aversive effects of cocaine might be a novel approach to fight cocaine dependence. In the second study, I studied cocaine-induced associative learning and changes in affect during cocaine conditioning and extinction. 50-kHz ultrasonic vocalizations (USVs) in rats are thought to reflect positive affect and occur upon appetitive stimuli and with cocaine delivery. First, I explored whether USVs might be elicited in anticipation of impending drug delivery. Shortly into conditioning, rats elicited USVs when placed in the cocaine-associated environment. USVs progressively increased, indicating a growing learned association between cocaine intake and cocaine-associated cues. This suggests that USVs may be a useful model for investigating cocaine craving and serve as a pharmacological target for interventions aimed to reduce cocaine craving and relapse. I then examined the effects of short-term deprivation of cocaine and cocaine cues on cocaine-conditioned USVs, which were both exaggerated after abstinence. The results may have clinical implications, in that intermittently avoiding cues or context may enhance drug cue salience and increase the probability of relapse. Motivational aspects of cocaine were assessed comparing commonly measured lever response rate and locomotion with cocaine-induced USVs during cocaine administration and extinction. In agreement with prevailing findings, lever responding for cocaine and cocaine-induced locomotor activity increased across conditioning sessions. However, the number of USVs evoked in response to cocaine infusion decreased with cocaine experience. These findings suggest growing tolerance to the rewarding properties of cocaine. These studies underscore the value of USV assessment during drug dependence studies.Item Burst timing-dependent plasticity of NMDA receptor-mediated transmission in midbrain dopamine neurons : a putative cellular substrate for reward learning(2009-08) Harnett, Mark Thomas; Morikawa, HitoshiThe neurotransmitter dopamine (DA) represents a neural substrate for positive motivation as its spatiotemporal distribution across the brain is responsible for goaldirected behavior and learning reward associations. The critical determinant of DA release throughout the brain is the firing pattern of DA-producing neurons. Synchronized bursts of spikes can be triggered by sensory stimuli in these neurons, evoking phasic release of DA in target brain areas to drive reward-based reinforcement learning and behavior. These bursts are generated by NMDA-type glutamate receptors (NMDARs). This dissertation reports a novel form of long-term potentiation (LTP) of NMDARmediated excitatory transmission at DA neurons as a putative cellular substrate for changes in DA neuron firing during reward learning. Patch-clamp electrophysiological recording from DA neurons in acute brain slices from young adult rats demonstrated that synaptic NMDARs exhibit LTP in an associative manner, requiring coordinated pre- and postsynaptic burst firing. Ca2+ signals produced by postsynaptic burst firing needed to be amplified by preceding metabotropic neurotransmitter inputs to effectively drive plasticity. Activation of NMDARs themselves was also necessary. These two coincidence detectors governed the timingdependence of NMDAR plasticity in a manner analogous to the timing rule for cuereward learning paradigms in behaving animals. Further mechanistic study revealed that PKA, but not PKC, activity gated LTP induction by regulating the magnitude of Ca2+ signal amplification via the inositol 1,4,5-triphospate (IP3) receptor and release of Ca2+ from intracellular stores. Plasticity of NMDARs was input specific and appeared to be expressed postsynaptically, but was not associated with a change in NMDAR subunit stoichiometry. LTP of NDMARs was DA-independent, and was specific for NMDARs: the same induction protocol produced long-term depression of AMPA receptors. NMDARs that had undergone LTP could be depotentiated in a spike-conditional manner, consistent with active unlearning. Finally, repeated, in vivo amphetamine experience dramatically increased facilitation of spike-evoked Ca2+ signals, which in turn drove enhanced plasticity. NMDAR plasticity thus represents a potential neural substrate for conditioned DA neuron burst responses to environmental stimuli acquired during reward-based learning as well a novel therapeutic target for intervention-based therapy of addictive disorders.Item COMT Genotype, Schizophrenia, and Dopamine Transmission(2011-02-01T19:33:08Z) Birchfield, Thomas Richard; Ghose, SubrotoCatechol-o-methyltransferase (COMT) catabolism is the primary mechanism for dopamine signal deactivation in the dorsolateral prefrontal cortex, an area of the brain associated with working memory. Working memory deficits are found in persons with schizophrenia and their unaffected siblings. A single nucleotide polymorphism of the COMT gene results in a MET-->VAL shift at codon 158, increased enzyme thermostability, and increased enzymatic activity. The hypothesized result of this shift is decreased dopamine transmission in the brain area associated with working memory due to increased dopamine catabolism. The current study analyzed the effect of COMT genotype and schizophrenia on the mRNA expression of genes known to be influenced by dopamine signal transmission with qPCR of RNA extracted from high-quality, fresh-frozen postmortem dorsolateral prefrontal cortex tissue. While no significant difference was observed between genotypes, a significant effect of diagnosis was found for the D1 dopamine receptor, COMT, and tyrosine hydroxylase, the rate-limiting step of dopamine synthesis. The current findings support a model decreased dopamine synthesis and increased catabolism leading to deficient dopamine signal transmission in persons with schizophrenia.Item Contracted spans of temporal integration in adults with attention deficit hyperactivity disorder(2011-12) Marusich, Laura Ranee; Gilden, David Loren, 1954-ADHD is a highly prevalent disorder in both children and adults that involves significant impairment throughout the lifespan, and yet the core cognitive deficits of the disorder are not well understood. Accumulating evidence of dysfunctioning dopamine systems motivated the theory that delay-of-reinforcement gradients are altered in ADHD in such a way that reinforcers must arrive earlier in time following a response for an association between the two to be learned. The current work is motivated by the conjecture that dopamine dysfunction has consequences for the maximum timescales over which connections can be formed, not just in reinforcement learning, but also in the processes of temporal integration and scene formation that allow humans to understand and navigate their world. There is a maximum window of temporal separation over which discrete events can be integrated into a unified experience, and the current experiments indicate that this maximum window of integration is contracted in ADHD. The experiments included multiple tasks designed so that the participant response required implicit integration over temporal intervals, and the length of those intervals was varied as an independent variable. Adults with and without ADHD completed these tasks, and the strength of temporal integration was measured with respect to interval length and compared between the two groups. This methodology was applied in five types of tasks: rhythmic tapping, spatial cuing, irrelevant feature priming, and two apparent motion tasks. On the whole, this suite of studies was successful in demonstrating a contraction in the maximum interval over which temporal integration can occur in ADHD relative to controls. Two of the tasks, rhythmic tapping and spatial cuing, generated unexpected and interesting results, and several follow-up tasks were designed to further explore these findings. As a result, a somewhat improved tapping task was discovered. This tapping task, as well as the irrelevant feature priming task and one of the apparent motion tasks, demonstrated potential utility for the diagnosis of adults with ADHD.Item Dopamine concentrations in the nucleus accumbens core-shell border during the early stages of operant ethanol self-administration(2010-12) Carrillo, Jennifer; Gonzales, Rueben Anthony; Harris, Adron; Duvauchelle, Christine L.; Morikawa, Hitoshi; Schallert, TimothyMesolimbic dopamine plays an important role in ethanol reinforcement, and studies have shown that accumbal dopamine increases during operant ethanol self-administration. However, no one has ever studied this dopaminergic response during the acquisition of ethanol self-administration. Furthermore, some studies have shown that the dopamine signal does not correlate with the pharmacological effects of ethanol, but with the time during which the animal consumes the majority of the ethanol solution and when the sensory stimuli of ethanol are strongest. However, there is currently no direct evidence showing that the sensory stimuli of ethanol is indeed what causes the brief increase in accumbal dopamine during ethanol self-administration. The studies in this dissertation attempted to elucidate these issues. We designed and tested a placebo spout, which was to be used to study the relationship between accumbal dopamine and the sensory stimuli of ethanol during self-administration. Unfortunately, the placebo designs were either not feasible for performing microdialysis or did not show promising behavioral data. We also developed and tested a self-administration protocol in which the concentrations of ethanol (10%) were kept constant throughout the study. The new protocol was successful in initiating and maintaining ethanol self-administration, and the animals doubled their intake from day 1 to day 2 of ethanol consumption. Using this protocol, we trained male Long Evans rats to self-administer ethanol and measured accumbal dopamine during the first two days of ethanol self-administration through microdialysis. The behavioral and neurochemical data matched. A single exposure to ethanol was sufficient for the animals to double their ethanol consumption by day 2 and to cause an increase in accumbal dopamine during the first 5 minutes of ethanol self-administration. The dopamine response was observed during the time when the sensory stimuli of ethanol were strongest, but before ethanol reached peak concentrations in the brain. Overall, these results suggest that the dopamine response to ethanol self-administration may not be solely pharmacological and that a single exposure to ethanol is sufficient to learn the association between ethanol and its cues. These findings give us greater insight into mesolimbic dopamine's role in the early stages of ethanol reinforcement.Item Dopamine responses in the ventral straitum contribute to ethanol preference and consumption and, mu opioid receptors do not mediate ethanol stimulated dopamine release(2010-08) Ramachandra, Vorani Sashrika; Gonzales, Rueben Anthony; Duvauchelle, Christine L.; Gore, Andrea C.; Bergeson, Susan; Morrisett, Richard A.; Ponomarev, IgorThe goal of this dissertation was two fold: 1) To relate dopamine responses in the ventral striatum to ethanol preference and consumption, and 2) to investigate the role of the mu opioid receptors in this ethanol induced dopamine release in the ventral striatum. First a two bottle choice experiment established that a substrain of C57BL/6 mice (C57BL/6NCrl) had significantly less preference for and consumption of ethanol than a second substrain of mouse based on the same background (C57BL6/J). The C57BL/6 strain has been extensively used in alcohol drinking studies and is well known for it’s propensity to consume alcohol over water. To determine if differences in ventral striatal dopamine response vii could contribute to this variability in drinking behavior, we characterized the dopamine response in both substrains of mice after intraperitoneal injections of 1.0, 2.0 or 3.0 g/kg ethanol or saline. We found that the acute intraperitoneal ethanol injections in naïve mice caused a significant elevation in dopamine in both substrains at all three doses with a significant difference between substrains at the two highest alcohol doses. Therefore, ethanol induced dopamine release in the ventral striatum may contribute to ethanol preference and consumption. Next, we investigated the effect of acute intraperitoneal ethanol injections on naïve mu opioid receptor knockout mice and in mice pretreated with a mu opioid receptor antagonist. The mice used were all established on the C57BL/6J background. We found that ventral striatal dopamine response was similar in these mice after 1.0, 2.0 and 3.0 g/kg intraperitoneal ethanol injections compared to appropriate controls. As both gene deletion and pharmacological blockade of the mu opioid receptor did not affect ethanol stimulated dopamine release, it points to the conclusion that this receptor may not play a significant role in ethanol induced ventral striatal dopamine release.Item Effects of auditory and thermal stimuli on 3,4- methylenedioxymethamphetamine (MDMA)-induced neurochemical and behavioral responses(2009-12) Feduccia, Allison Anne; Duvauchelle, Christine L.The amphetamine derivative, 3,4-methylenedioxymethamphetamine (MDMA), is a popular drug often taken by young adults at dance clubs or rave parties. Laser light shows, fast-paced electronic music, and hot crowded dance floors are characteristic of these events, and Ecstasy users report that the acute effects of the drug are potentiated by these stimulatory conditions. However, it remains largely unknown how environmental stimuli impact the neurochemical and physiological effects of MDMA. The aim of the first study presented in this dissertation was to investigate how auditory stimuli (music, white noise, and no additional sound) influence MDMA conditioned place preference (CPP), self-administration, and nucleus accumbens (NAcc) dopamine (DA) and serotonin (5-HT) responses. Findings revealed a significant CPP for animals exposed to white noise during MDMA conditioning trials. After self-administration of MDMA (1.5 mg/kg), NAcc DA and 5-HT were highest in rats exposed to music during the test session. The second study aimed to investigate the effects of ambient temperature (23°or 32°C) on long-term MDMA self-administration and neurochemical responses. Results indicated no difference in self-administration or locomotor activity rates for the high versus room temperature groups across sessions. However, MDMA (3.0 mg/kg) administered in high ambient temperature resulted in significantly greater NAcc serotonin release compared to when taken at room temperature, but no differences in dopamine response was determined between the two conditions. Overall, these results indicate that auditory and thermal stimuli can effect MDMA-induced behavioral and neurochemical responses. The last aim tested a novel apparatus and method for use in animal models of drug reinforcement. By combining traditional CPP and self-administration procedures, this approach provided more informative data and circumvented some inherent drawbacks of each method alone. In addition to confirming the ability to produce drug conditioned place preferences after short- and long-term experiments, the long-term version of the procedure revealed a significant positive relationship between lever response rate and CPP magnitude. Therefore, this experimental design can be used to identify subgroups of rats that may vary in sensitivity to drug motivational effects. Further study of these populations may be useful in the development of behavioral and pharmacological therapies for drug addiction.Item Ethanol experience induces metaplasticity of NMDA receptor-mediated transmission in ventral tegmental area dopamine neurons(2011-08) Bernier, Brian Ernest; Morikawa, Hitoshi; Harris, R. A.; Aldrich, Richard; Koester, Helmut; Valenzuela, FernandoAddiction is thought to arise, in part, from a maladaptive learning process in which enduring memories of drug-related experiences are formed, resulting in persistent and uncontrollable drug-seeking behavior. However, it is well known that both acute and chronic alcohol (ethanol) exposures impair various types of learning and memory in both humans and animals. Consistent with these observations, both acute and chronic exposures to ethanol suppress synaptic plasticity, the major neural substrate for learning and memory, in multiple brain areas. Therefore, it remains unclear how powerful memories associated with alcohol experience are formed during the development of alcoholism. The mesolimbic dopaminergic system is critically involved in the learning of information related to rewards, including drugs of abuse. Both natural and drug rewards, such as ethanol, cause release of dopamine in the nucleus accumbens and other limbic structures, which is thought to drive learning by enhancing synaptic plasticity. Accumulating evidence indicates that plasticity of glutamatergic transmission onto dopamine neurons may play an important role in the development of addiction. Plasticity of NMDA receptor (NMDAR)-mediated transmission may be of particular interest, as NMDAR activation is necessary for dopamine neuron burst firing and phasic dopamine release in projection areas that occurs in response to rewards or reward-predicting stimuli. NMDAR plasticity may, therefore, drive the learning of stimuli associated with rewards, including drugs of abuse. This dissertation finds that repeated in vivo ethanol exposure induces a metaplasticity of NMDAR-mediated transmission in mesolimbic dopamine neurons, expressed as an increased susceptibility to the induction of NMDAR LTP. Enhancement of NMDAR plasticity results from an increase in the potency of inositol 1,4,5- trisphosphate (IP3) in producing the facilitation of action potential-evoked Ca2+ signals critical for LTP induction. Interestingly, amphetamine exposure produces a similar enhancement of IP3R function, suggesting this neuroadaptation may be a common response to exposure to multiple drugs of abuse. Additionally, ethanol-treated mice display enhanced learning of cues associated with cocaine exposure. These findings suggest that metaplasticity of NMDAR LTP may contribute to the formation of powerful memories related to drug experiences and provide an important insight into the learning component of addiction.Item Gait transitions in C. elegans(2013-12) Topper, Stephen Matthew; Pierce-Shimomura, Jonathan T.The ability to switch between different forms of locomotion is critical to many aspects of survival, whether it is switching from walking to running to evade predators, or switching to a slower gait to obtain food. Uncovering the mechanisms behind gait transitions has implications for many fields, from treating Parkinson Disease to understanding the impact of drugs of abuse on movement. However, the mechanisms of gait transitions are not well understood. The experiments outlined in this thesis sought to understand the neuronal basis for gait switching. This work employed the nematode Caenorhabditis elegans, a unique model organism chosen for its genetic tractability and fully characterized nervous system. C. elegans displays different forms of motion: crawling on land and swimming in liquid. First, I sought to determine the mechanisms for switching between these forms of motion in collaboration with Dr. Andres Vidal-Gadea. In the process, we discovered that crawling and swimming actually represent distinct gaits in contrast to recent reports that suggested they were merely a single gait. We further elucidated mechanisms for gait transition in C. elegans. For instance, we found that the transition to crawling required viii the D1-like dopamine receptors DOP-1 and DOP-4; and activation of dopamine neurons via the light-activated cation channel Channelrhodopsin2 was sufficient to induce crawling behavior in worms immersed in liquid. Conversely, photoactivation of serotonergic neurons expressing Channelrhodopsin2 induced swim-like behavior on land. Finally, laser microablation of dopaminergic or serotonergic neurons was sufficient to impair the transition to crawl or swim, respectively. Together these results show that transitions to crawling and swimming are controlled by dopamine and serotonin respectively. Next I wanted to better understand how gait transitions are impaired by a drug of abuse, alcohol. I found that, as in other organisms, ethanol disrupts gait transitions, causing worms in water to inappropriately transition from swim to crawl and to display other land-specific behaviors. Animals lacking the D1-like dopamine receptor DOP-1 were resistant to the ethanol-induced transition to crawl. Finally, I found that several interneurons required for the transition to crawl. Specifically, laser microablation of the DOP-4 receptor-expressing neuron RID or the DOP-1-expressing neurons PQR or RIS resulted in a significant impairment in the time to crawl onset. Overall, the findings presented in this thesis represent the first evidence that C. elegans uses an evolutionarily conserved mechanism to transition between gaits and provides the beginning of a molecular description of gait transitions.Item Mechanisms underlying the dysregulation of postural stability in dopamine-depleted rates(2008-05) Woodlee, Martin Thomas, 1977-; Schallert, TimothyThe work described in this dissertation aims to understand how postural instability (PI), a troubling symptom of advanced Parkinson's disease (PD) in humans, develops from the degeneration of nigrostriatal dopamine neurons characteristic of PD. The studies herein (1) outline the development of clinically relevant methods for evaluating PI in experimental rodents, (2) indicate that PI may not result directly from disruption of dopamine systems but may instead arise from non-dopaminergic changes that occur subsequent to dopamine depletion, and (3) search for specific evidence of plasticity or degeneration outside of the damaged nigrostriatal dopamine system that may be linked to the development of PI. It is hoped that this work will help lay the foundation for the development of novel prophylactic treatments aimed at preventing the progression of PD to advanced stages where treatment-resistant symptoms such as PI appear.Item Medial prefrontal cortical extracellular dopamine responses after acutely experimenter-administered or orally self-administered ethanol(2012-12) Schier, Christina Joanne; Gonzales, Rueben AnthonyDopamine signaling in the prefrontal cortex is thought to play a role in ethanol abuse. However, little is known about how ethanol affects dopamine signaling in the region. There are a few rodent studies regarding the matter, but both the pharmacological effects of ethanol and the effects of self-administered ethanol on extracellular dopamine in the medial prefrontal cortex remain unclear. The goal of the studies conducted for this dissertation is to clarify these relationships. To accomplish this, we monitored both dialysate dopamine and ethanol concentrations in the medial prefrontal cortex of Long Evans rats while an experimenter administered or a rat operantly self-administered ethanol. In naïve rats, dopamine dose-dependently increased after the intravenous infusions of a 10% ethanol solution, while no changes were noted after saline infusions. In rats trained to orally self-administer drinking solutions, dopamine transiently increased at the initiation of consumption in both ethanol-plus-sucrose- and sucrose-solution-consuming rats. Dopamine concentrations remained significantly elevated for the entire 21-minute drinking period in the ethanol-plus-sucrose-consuming group and for the first seven minutes of the drink period in the sucrose-consuming group. Additionally, in the ethanol-plus-sucrose-consuming group, dialysate ethanol concentrations were lowest at the initiation of drinking and then slowly increased, peaking 35 minutes after drinking commenced. Taken together, these data suggest that the mesocortical dopamine system is responsive to acute, intravenous and repeatedly, orally, self-administered ethanol. It appears that direct pharmacological effects of ethanol were responsible for the dopamine increase after acute, ethanol administration. Furthermore, while is it possible that the direct pharmacological effects of ethanol also bolstered the dopamine response seen after ethanol self-administration, we cannot firmly conclude by what mechanism ethanol elicited the differences. Overall, our clarifying and novel results support a role for the mesocortical dopamine system in ethanol abuse, which deserves continued investigation. In addition to completing the two aforementioned data studies, we also published the methods we use to monitor dialysate ethanol concentrations, in a specific brain region, during ethanol self-administration in a video-methods journal. The methods are presented in both a detailed written protocol, as well as a video demonstrating how to perform the procedures.Item Regulation of the dopamine transporter: a role for ethanol and protein interactions(2004) Maiya, Rajani Padmanabh; Harris, R. AdronItem A role for the medial preoptic area in mediating a response to cocaine(2014-12) Tobiansky, Daniel Jonathan; Dominguez, Juan M.The salience of natural or drug-associated reward is mediated by phasic dopamine (DA) release in the nucleus accumbens (NAc) arising from DAergic cells in the ventral tegmental area (VTA). Circulating sex steroid hormones can modulate reward associated with drugs of abuse; yet, it still remains unclear which brain regions are responsible for this modulation. The medial preoptic area (mPOA) is a hypothalamic brain area involved in the expression of naturally rewarding behaviors as well as the regulation and reception of circulating sex steroid hormones in female rats. Considering its role in regulating naturally rewarding behaviors, its well-established anatomical connectivity with the VTA, and its responsiveness to circulating sex steroid hormones, the mPOA is an ideal neural node through which hormones could modulate the rewarding facets of drugs of abuse. Here I show that preoptotegmental efferents to the VTA are primarily GABAergic, that they appose putative DAergic cell bodies in the VTA that project to the NAc, and that they are capable of responding to sex steroid hormones and changes in DA release. Furthermore, cocaine influences neural activity in mPOA efferents that project to the VTA. Removal of the mPOA also enhanced cocaine-induced locomotion, Fos-immunoreactivity in the mesolimbic reward system, DA release in the NAc, and augmented conditioned place preference. Together these findings suggest that the mPOA modulates the release of DA in the mesolimbic reward circuitry via inhibitory connections with DA neurons residing in the VTA, and sex steroid hormones, in turn, may act in the mPOA to modulate response to cocaine.Item ROLE OF AGE-ASSOCIATED OXIDATIVE STRESS IN ALTERED RENAL D1 AND AT1 RECEPTOR FUNCTIONS AND HYPERTENSION(2012-04-19) Chugh, Gaurav; Lokhandwala, Mustafa F.; Asghar, Mohammad; Hussain, Tahir; Prince, Randall A.; Shek, EugeneBlood pressure (BP) and oxidative stress increase with aging. Renal dopamine D1 (D1R) and angiotensin AT1 (AT1R) receptors by maintaining sodium homeostasis regulate blood pressure. Impaired D1R and exaggerated AT1R functions in the kidneys contribute to hypertension in animal models, which also exhibit oxidative stress. However, the role of oxidative stress in age-related hypertension has not been studied. In this study, we hypothesized that age-associated increase in oxidative stress by altering renal D1R and AT1R functions cause high BP in aging. To test this hypothesis, we measured oxidative stress, BP, and D1 and AT1 receptor functions in adult (3-month) and old (21-month) Fischer 344 X Brown Norway F1 (FBN) rats supplemented without/with antioxidant tempol. We found age-related increases in oxidative stress and blood pressure; which were reduced with tempol treatment in old FBN rats. D1R and AT1R functions were determined by measuring diuretic and natriuretic responses to SKF-38393 (D1R agonist) and candesartan (AT1 receptor antagonist) respectively. Natriuresis in response to D1R activation was impaired in old rats, suggesting an age-associated decline in D1R function in old FBN rats. Increase in G protein coupled receptor kinase (GRK) expression/activity is associated with reduced D1R-G protein coupling and function in humans and animal models with hypertension. We found age-associated increase in GRK-4 levels accompanied with D1R-G protein uncoupling in the renal proximal tubules of old FBN rats. Tempol treatment reduced GRK-4 levels and restored D1R-G protein coupling in these old rats. Natriuretic and diuretic responses to candesartan; however, were exaggerated in old rats, suggesting an age-associated increase in renal AT1R function in old FBN rats. Age-related increases in angiotensin II-mediated G protein coupling leading to exaggerated Na,K-ATPase activity may have caused increased renal AT1R function observed in old FBN rats. Tempol treatment restored angiotensin II-mediated G protein coupling and Na,K-ATPase response and thus reduced candesartan-mediated natriuresis and diuresis in old FBN rats. Our results demonstrate that both diminished renal D1R and exaggerated AT1R functions are associated with high BP in old FBN rats. Furthermore, oxidative stress may cause altered renal D1R and AT1R functions and high BP in these old rats.Item The Role of CLOCK in Regulation of Dopamine Neurotransmission in the CLOCKdelta19 Mutant Mouse Model(2012-07-17) Spencer, Sade Monique; McClung, Colleen A.Mice with a mutation in the circadian gene Clock (Clockdelta19) display a behavioral profile which parallels a euphoric manic-like state including hyperactivity, disrupted activity rhythms, increased substance abuse vulnerability, and decreases in anxiety and depression-related behavior. The molecular clock has significant cross-talk with many of the brain’s neurotransmitter systems. The purpose of this dissertation is to characterize the role of CLOCK in regulating dopamine transmission in mood and reward-related circuits. We present a mechanism by which CLOCK regulates dopaminergic activity in the mesoaccumbens circuit and contributes to anxiety-related behavior. In vivo recording of ventral tegmental area (VTA) dopamine cells throughout the 24 hour cycle revealed that firing and bursting was elevated in Clockdelta19 mutants with the most significant deviations early in the light cycle. Mimicking this increase in dopaminergic activity using optogenetic targeting resulted in decreased anxiety-related behavior similar to the Clockdelta19 phenotype. Consistent with the electrophysiological findings, tyrosine hydroxylase (TH) mRNA and protein was elevated in the VTA in a daytime-specific manner leading to increased dopamine synthesis in the nucleus accumbens. CLOCK binding was detected at E-box elements within the TH promoter with greater enrichment observed during the light phase when TH expression is low. These results suggest a negative regulation of TH by CLOCK. To examine alterations in the nigrostriatal dopamine circuit, HPLC measurements of dopamine and metabolites were performed in the dorsal striatum revealing significant increases in DOPAC and HVA. Dopamine receptor agonists and antagonists were used to pharmacologically probe dopamine receptor function. An enhancement of the locomotor suppressing response to dopamine antagonists in Clockdelta19 mice suggested increased dopaminergic tone. Clockdelta19 mice were insensitive to the locomotor stimulating effects of a D1 agonist, but displayed increased levels of D1DR protein. Conversely, the Clockdelta19 mutants displayed enhanced locomotor suppression to a D2 agonist and a coincident increase in D2DR protein. Forskolin stimulation of cAMP resulted in blunted molecular responses in the Clockdelta19 mutants consistent with impairments in D1 signaling and/or enhancements in D2 signaling. In summary, normal CLOCK function appears to be involved in the regulation of dopamine transmission in the striatum. [Keywords: circadian rhythms; dopamine; CLOCK; bipolar disorder; dopamine receptors; tyrosine hydroxylase; ventral tegmental area]Item The pharmacological effects of acute ethanol on catecholamines in the medial prefrontal cortex and dorsal striatum(2016-12) Vena, Ashley; Gonzales, Rueben Anthony; Dominguez, Juan; Harris, Adron; Duvauchelle, Christine; Morrisett, RichardThe dorsal striatum and the medial prefrontal cortex are part of a neurocircuitry that is affected by acute and chronic drug use. In the present studies, we sought to characterize the pharmacological effects of ethanol on extracellular catecholamine concentrations in the dorsal striatum and medial prefrontal cortex. To this end, we utilized two different routes of administration to quantify ethanol’s actions. We performed in vivo microdialysis in adult, male Long Evans rats as they received single or repeated intravenous infusions of ethanol. Following infusion of a 1-g/kg dose of ethanol, we observed no significant effects on extracellular dopamine in either the dorsomedial or dorsolateral striatum, but in a separate group of animals, we observed significant stimulation of extracellular norepinephrine in the medial prefrontal cortex. However, following a cumulative intravenous dosing protocol, we observed a gradual ramping up of tonic dopamine activity in the dorsal striatal subregions, which was more robust in the dorsomedial striatum. Subsequently, we performed in vivo microdialysis in separate groups of rats during an operant self-administration session to quantify the time course of extracellular dopamine and norepinephrine in the medial prefrontal cortex. In the seven operant sessions prior to the microdialysis test session, each group of rats had been assigned to a separate treatment group: one that received a sweetened ethanol solution, one that received a sucrose solution, and a handling control group that did not receive any drinking solutions. In the ethanol-experienced animals, we report a reduction in basal dopamine and norepinephrine in the medial prefrontal cortex, relative to control groups. However, there were no significant differences in the temporal profile of extracellular norepinephrine across the three treatment groups. These studies demonstrate that limited voluntary ethanol consumption appears to be sufficient to alter tonic catecholamine signaling in the medial prefrontal cortex. Additionally, we conclude that central catecholamine signaling pathways are a target for ethanol.