Pathological gambling is a serious disorder with lifetime prevalence between 1.1-3.5%. Evidence suggests commonalities in the neurochemical basis of pathological gambling and psychostimulant addiction. However, parallel effects of gambling and a stimulant drug have not been assessed in the same subjects. This study employed a cross-priming strategy in which 12 male pathological gamblers and 11 male controls were exposed to a 15-minute slot machine game and d-amphetamine (0.4 mg/kg). Subjective, cognitive, electrophysiological, and physiological responses were assessed. Gamblers reported greater desire to gamble after both reinforcers, when baseline motivation was controlled. Conversely, gamblers exhibited diminished cardiovascular response to amphetamine. Gamblers also exhibited decreased pre-pulse inhibition (impaired sensorimotor gating), and deficits on this index predicted greater post-amphetamine desire to gamble and decreased heart rate response to the dose. Results are consistent with possible dopaminergic sensitization in pathological gamblers, but also suggest that central noradrenergic receptor deficits contribute importantly to these effects.

Pathological gambling is a serious disorder with lifetime prevalence between 1.1-3.5%. Evidence suggests commonalities in the neurochemical basis of pathological gambling and psychostimulant addiction. However, parallel effects of gambling and a stimulant drug have not been assessed in the same subjects. This study employed a cross-priming strategy in which 12 male pathological gamblers and 11 male controls were exposed to a 15-minute slot machine game and d-amphetamine (0.4 mg/kg). Subjective, cognitive, electrophysiological, and physiological responses were assessed. Gamblers reported greater desire to gamble after both reinforcers, when baseline motivation was controlled. Conversely, gamblers exhibited diminished cardiovascular response to amphetamine. Gamblers also exhibited decreased pre-pulse inhibition (impaired sensorimotor gating), and deficits on this index predicted greater post-amphetamine desire to gamble and decreased heart rate response to the dose. Results are consistent with possible dopaminergic sensitization in pathological gamblers, but also suggest that central noradrenergic receptor deficits contribute importantly to these effects.

Drug abuse peaks during adolescence, and exposure to drugs during adolescence predicts drug abuse in adulthood. Nevertheless, adolescence is not widely studied in animal models of drug intake. Moreover, few studies have investigated sex differences in drug-reinforced behavior during adolescence. We studied age- and sex-differences in acquisition and maintenance of amphetamine self-administration in Sprague-Dawley rats. Adolescent males took more amphetamine than adult males, supporting the hypothesis that adolescents are more sensitive to amphetamine. A high rate of “inappropriate” active lever presses among periadolescent males suggests impulsive behavior. In the maintenance phase of testing, young adult males failed to work as hard as adult males. In contrast, young adult females worked harder than adult females. Comparing sex groups, young adult females worked harder than age-matched males to obtain amphetamine. These results will ultimately help to form effective treatment and prevention programs for drug dependent individuals of all ages and both sexes.

Uncoupling proteins (UCPs) are highly conserved inner mitochondrial membrane proteins that have been found in plants, nematodes, flies, and vertebrates. UCPs dissipate the proton gradient formed by the electron transport chain in an energy-expending process that generates heat. In mammals, the brown fat-specific UCP1 is thought to be the dominant, if not the only significant mediator of thermogenic responses. However, adult humans express only negligible amounts of brown fat and UCP1, yet still show significant non-shivering thermogenic responses (e.g. amphetamine-induced hyperthermia, diet induced thermogenesis, fever). Thus, the fact that human thermogenic mechanisms haven't been identified is a huge gap in our understanding of human thermoregulation. UCP3 is primarily expressed in skeletal muscle, an established thermogenic organ which is a major target of amphetamine-induced pathology. UCP3 knockout mice have a near complete loss (~80%) of amphetamine-induced thermogenesis and are completely protected from amphetamine-induced death over a range of lethal doses. With regard to mechanisms of UCP3 activation, we observed that norepinephrine and free fatty acids are elevated in the bloodstream prior to peak amphetamine-induced hyperthermia. However, little is known about the anatomic location of UCP3-dependent thermogenesis or the mechanisms by which fatty acids regulate UCP function. Thus, we sought to investigate the physiology and biochemical activation of UCP3 to establish the thermogenic potential of skeletal muscle uncoupling and elucidate the mechanisms of UCP3 function. The overall goal of this research was to identify the tissue target(s) and mechanisms involved in amphetamine-induced UCP3-dependent thermogenesis. Herein, we show that in addition to a deficit in induced thermogenesis, UCP3-null mice also lack responses to other physiologically-relevant stimuli (i.e. catecholamines and bacterial pathogens). Conversely, UCP3 knockout mice, engineered to express UCP3 only in skeletal muscle have an augmented thermogenic response to amphetamines. In order to explore UCP3's mechanism of activation, we performed a modified yeast two-hybrid analysis and identified [Delta][superscript 3,5][Delta][superscript 2,4]dienoyl-CoA isomerase (DCI) as a UCP3 binding partner. DCI, an auxiliary fatty acid oxidation enzyme, protects cells from the accumulation of toxic lipid metabolites. Using immunoprecipitation and fatty acid oxidation (FAO) assays, we determined that UCP3 and DCI directly bind in the mitochondrial matrix in order to augment lipid metabolism. These findings support a novel model in which skeletal muscle UCP3 is responsible for inducible thermogenesis through cooperation with binding partners such as DCI which enhance oxidation of fatty acids. Together, these studies shed light on thermogenic pathways in rodents that are likely to be relevant to humans. / text

Indiana University-Purdue University Indianapolis (IUPUI) / Striatal-mediated pathological disease-states such as Obsessive-Compulsive Disorder (OCD), Parkinson’s Disease (PD), and psychostimulant drug addiction/abuse are coupled with distinct motor movement abnormalities. In addition, these disorders are associated with perturbed synaptic transmission. Proper synaptic transmission is critical for maintaining neuronal communication. Furthermore, in many striatal-dependent disease-states, the principle striatal neurons, medium spiny neurons (MSNs), exhibit differential perturbations in downstream signaling. Signal transduction pathways that are localized to the glutamatergic post-synaptic density (PSD) of GABAergic MSNs regulate protein phosphorylation in a tightly controlled manner. Alterations in the control of this phosphorylation in striatal MSNs are observed in myriad striatal pathological diseasestates and can give rise to perturbations in synaptic transmission. While serine/threonine kinases obtain substrate specificity, in part, by phosphorylating specific consensus sites, serine/threonine phosphatases such as protein phosphatase 1 (PP1) are much more promiscuous. To obtain substrate selectivity, PP1 associates with targeting proteins. The major targeting protein for PP1 in the PSD of striatal dendritic spines is spinophilin. Spinophilin not only binds PP1, but also concurrently interacts with myriad synaptic proteins. Interestingly, dopamine depletion, an animal model of PD, modulates spinophilin protein-protein interactions in the striatum. However, spinophilin function on basal striatal-mediated motor behaviors such as the rotarod or under hyperdopaminergic states such as those observed following psychostimulant-induced behavioral sensitization are less well characterized. To elucidate spinophilin function more specifically, we have generated multiple transgenic animals that allow for cell type-specific loss of spinophilin as well as cell-specific interrogation of spinophilin protein interactions. Here, I report the functional role of spinophilin in regulating striatal mediated motor behaviors and functional changes associated with amphetamine-induced locomotor sensitization. In addition, we define changes in spinophilin protein-protein interactions that may mediate these behavioral changes. Furthermore, global loss of spinophilin abrogates amphetamine-induced sensitization and plays a critical role in striatal motor learning and performance. The data suggest that the striatal spinophilin protein interactome is upregulated in MSNs following psychostimulant administration. In addition, loss of spinophilin changes protein expression in myriad psychostimulant-mediated striatal adaptations. Taken together the data suggests that spinophilin’s protein-protein interactions in the striatum are obligate for appropriate striatal mediated motor function.

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Indiana University-Purdue University Indianapolis (IUPUI) / The striatum is a key brain region involved in regulating motor output and integration. The dorsal and ventral subdivisions of the striatum work in concert to mediate the reinforcing and motor behavioral outputs of the striatum. Moreover, dysfunction of these striatal regions is involved in various diseases including Parkinson’s disease and drug addiction. Therefore, understanding and characterizing biochemical and molecular changes within the striatum associated with these diseases is key in devolving novel therapeutics to treat these disease states. The main output neurons of the striatum are GABAergic, medium-spiny neurons (MSNs), and striatal functionality is mediated by neuroplastic changes in MSN activity. Within MSNs, dopaminergic receptor activation triggers a cascade of reversable phosphorylation, which is facilitated by the activation of specific protein kinases and inhibition of specific protein phosphatases. In comparison to the 350 serine/threonine protein kinases expressed within the striatum, there are only 40 major serine/threonine protein phosphatases. However, serine/threonine protein phosphatases, such as protein phosphatase 1 (PP1), gain their target specificity by interacting with phosphatase-targeting proteins. Within the striatum, the neurabins, termed neurabin and spinophilin, are the most abundant PP1 targeting proteins in dendritic spines. Spinophilin’s expression in the striatum has been strongly characterized, and spinophilin has been shown to regulate striatal-dependent motor-skill learning and amphetamine-induced locomotor sensitization. In contrast to spinophilin, neurabin’s expression within the striatum and its involvement in these striatal-dependent behaviors has not been fully probed. I found that neurabin expression in the striatum is not sex-dependent but is age-dependent. In addition to these data, I also present validation of new global, constitutive and conditional neurabin knock-out mouse lines. Finally, I present data that, unlike previous studies in spinophilin knockout mice, neurabin knockout mice have enhanced striatal-dependent motor-skill learning, but do not impact amphetamine-induced locomotor sensitization. Further characterization of neurabin’s expression in the striatum, and its role in these key striatal behaviors could provide a druggable target for therapeutics designed to address striatal dysfunction.

Master of Science / Department of Psychological Sciences / Mary Cain / Novelty-seeking and sensation-seeking are traits implicated in initial drug experimentation and relapse in human populations. To research the neurobiological substrates that are implicated in novelty/sensation-seeking that predispose an individual to drug use, a rodent model was used. Recently, 50 kHz ultrasonic vocalizations (USV) have been identified as indices of affective state and are evoked by several drugs of abuse, specifically when these drugs of abuse have their pharmacological effects in the mesolimbic dopamine path. Secondly, genetic breeding of high and low vocalizers suggests not only are they different in the calling frequency, but also to drug sensitivity, suggesting ultrasonic vocalizations may be a behavioral marker for individual differences in the mesolimbic dopamine circuit. Two sensation/novelty seeking screens and an ultrasonic vocalization screen were used in rats to predict the locomotor and 50 kHz USV response to a low (.3 mg/kg) and high dose (1.0 mg/kg) of amphetamine. Correlation analysis revealed none of the novelty screens were correlated. Simultaneous regression analyses indicated amphetamine dose-dependently increased locomotor activity acutely and chronically but did not increase 50 kHz USV. The USV assessment predicted USV response to amphetamine acutely and chronically but was not dose dependent. No interactions among any predictors were observed. Previous research has dichotomized the novelty/sensation-seeking trait and found significant differences between high and low novelty responders. The current research provides evidence for maintaining continuous individual difference variables, and suggests each screen measures a different trait implicated in addiction.

The results of the study showed that D-Amphetamine had a significant effect on the acquisition of the active avoidance conditioning (CAR).