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Charles W. Bradberry

Bio: Charles W. Bradberry is an academic researcher from University of Pittsburgh. The author has contributed to research in topics: Dopamine & Microdialysis. The author has an hindex of 29, co-authored 58 publications receiving 3076 citations. Previous affiliations of Charles W. Bradberry include Yale University & Veterans Health Administration.


Papers
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Journal ArticleDOI
01 Jan 1997-Synapse
TL;DR: The measure of amphetamine‐induced dopamine release with SPECT in nonhuman primates is validated and the use of this SPECT paradigm as a noninvasive measurement of intrasynaptic dopamine release in the living brain is validated.
Abstract: The competition between endogenous transmitters and radiolabeled ligands for in vivo binding to neuroreceptors might provide a method to measure endogenous transmitter release in the living human brain with noninvasive techniques such as positron emission tomography (PET) or single photon emission computerized tomography (SPECT). In this study, we validated the measure of amphetamine-induced dopamine release with SPECT in nonhuman primates. Microdialysis experiments were conducted to establish the dose-response curve of amphetamine-induced dopamine release and to document how pretreatment with the dopamine depleter alpha-methyl- para-tyrosine (aMPT) affects this response. SPECT experiments were performed with two iodinated benzamides, ( 123 I)IBZM and ( 123 I)IBF, under sustained equilibrium condition. Both radiotracers are specific D2 antagonists, but the affinity of ( 123 I)IBZM (KD 5 0.4 nM) is lower than that of ( 123 I)IBF (KD 5 0.1 nM). With both tracers, we observed a prolonged reduction in binding to D2 receptors following amphetamine injection. ( 123 I)IBZM binding to D2 receptors was more affected than ( 123 I)IBF by high doses of amphetamine, indicating that a lower affinity increases the vulnerability of a tracer to endogenous competition. With ( 123 I)IBZM, we observed an excellent correlation between reduction of D2 receptor binding measured with SPECT and peak dopamine release measured with microdialysis after various doses of amphetamine. Pretreatment with aMPT significantly reduced the effect of amphetamine on ( 123 I)IBZM binding to D2 receptors, confirming that this effect was mediated by intrasynaptic dopamine release. Together, these results validate the use of this SPECT paradigm as a noninvasive measurement of intrasynaptic dopamine release in the living brain. Synapse 25:1-14,

266 citations

Journal ArticleDOI
TL;DR: In rats, EC and cocaine each increased locomotor activity and rearing to the same extent following i.p. administration, and in self-administration studies in primates, EC was approximately equipotent to cocaine in maintaining responding.

247 citations

Journal ArticleDOI
TL;DR: In vivo microdialysis measurements of extracellular dopamine were made simultaneously in nucleus accumbens (NAS) and ventral tegmental area (VTA) in anesthetized rats and the relevance of the observed effects to reported effects of cocaine on firing rate of mesoaccumbens DA neurons is discussed.

196 citations

Journal ArticleDOI
TL;DR: Data indicate an association of psychostimulant use with IIR activation in the brain even at exposures not traditionally associated with neurotoxicity, suggesting the gradually escalating deleterious effects of psychOSTimulants use could in part involve neuroinflammatory mechanisms.
Abstract: During the past two decades, there has been a tremendous expansion of knowledge regarding the neurobiological effects of substance abuse and how these effects impact behavior. At the same time, there has been a profound change in our understanding of the way in which the central nervous system responds to noxious stimuli. Most often referred to as the innate immune response (IIR), this defense mechanism is activated by a number of agents (toxic, microbial, ischemic) and has been implicated in the progression of a number of neurodegenerative diseases. We review evidence that psychostimulants of abuse (cocaine, methamphetamine, ecstasy) are associated with activation of the IIR. We first present background on what is currently known about the IIR including some of the cellular elements involved (microglia, astrocytes, vascular endothelial cells), key receptor pathways, and primary inflammatory cytokines (IL-1β, IL-6, TNF-α). We then present a variety of protein and gene expression data taken from animal studies that show increased expression of various components of the IIR following acute or repeated psychostimulant administration. Collectively the data indicate an association of psychostimulant use with IIR activation in the brain even at exposures not traditionally associated with neurotoxicity. Thus, the gradually escalating deleterious effects of psychostimulant use could in part involve neuroinflammatory mechanisms. Finally, we offer one hypothesis of a possible mechanism by which psychostimulants result in IIR activation and discuss the potential therapeutic implications of these findings for treatment of the recovering addict.

168 citations

Journal ArticleDOI
TL;DR: It is confirmed in vivo that cocaethylene is more selective in its actions than cocaine with respect to dopamine and serotonin uptake, and route‐dependent differences in attainment of brain drug levels have been observed that may impact on interpretations of the relative potency of the reinforcement value of these compounds.
Abstract: Cocaethylene is a pharmacologically active metabolite resulting from concurrent cocaine and ethanol consumption. The effects of cocaine and cocaethylene on extracellular levels of dopamine in the nucleus accumbens, and serotonin in the striatum were characterized in vivo in the anesthetized rat. Both intravenous (3 mumol/kg) and intraperitoneal (44 mumol/kg) routes of administration were used. In addition to monitoring neurotransmitter levels, microdialysate levels of cocaine and cocaethylene were determined at 4-min intervals after intravenous administration, and at 20-min intervals after intraperitoneal administration. Extracellular levels of dopamine in the nucleus accumbens were increased to approximately 400% of preinjection value by both cocaine and cocaethylene when administered intravenously. Cocaine caused a significant increase of striatal serotonin to 200% preinjection value, whereas cocaethylene had no effect. Brain levels of cocaine and cocaethylene after intravenous administration did not differ. After intraperitoneal administration, extracellular levels of dopamine in the nucleus accumbens were increased to 400% of preinjection levels by cocaine, but were only increased to 200% of preinjection levels by cocaethylene, the difference being statistically significant. Serotonin levels were increased to 360% of preinjection levels by cocaine, but only to 175% of preinjection value by cocaethylene. Levels of cocaine attained in brain were significantly higher than those for cocaethylene, suggesting pharmacokinetic differences with the intraperitoneal route. These results confirm in vivo that cocaethylene is more selective in its actions than cocaine with respect to dopamine and serotonin uptake. In addition, route-dependent differences in attainment of brain drug levels have been observed that may impact on interpretations of the relative potency of the reinforcement value of these compounds.

157 citations


Cited by
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TL;DR: S sensitization of incentive salience can produce addictive behavior even if the expectation of drug pleasure or the aversive properties of withdrawal are diminished and even in the face of strong disincentives, including the loss of reputation, job, home and family.

6,783 citations

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TL;DR: The dopamine hypothesis of schizophrenia-version III is synthesized into a comprehensive framework that links risk factors, including pregnancy and obstetric complications, stress and trauma, drug use, and genes, to increased presynaptic striatal dopaminergic function.
Abstract: The dopamine hypothesis of schizophrenia has been one of the most enduring ideas in psychiatry. Initially, the emphasis was on a role of hyperdopaminergia in the etiology of schizophrenia (version I), but it was subsequently reconceptualized to specify subcortical hyperdopaminergia with prefrontal hypodopaminergia (version II). However, these hypotheses focused too narrowly on dopamine itself, conflated psychosis and schizophrenia, and predated advances in the genetics, molecular biology, and imaging research in schizophrenia. Since version II, there have been over 6700 articles about dopamine and schizophrenia. We selectively review these data to provide an overview of the 5 critical streams of new evidence: neurochemical imaging studies, genetic evidence, findings on environmental risk factors, research into the extended phenotype, and animal studies. We synthesize this evidence into a new dopamine hypothesis of schizophrenia-version III: the final common pathway. This hypothesis seeks to be comprehensive in providing a framework that links risk factors, including pregnancy and obstetric complications, stress and trauma, drug use, and genes, to increased presynaptic striatal dopaminergic function. It explains how a complex array of pathological, positron emission tomography, magnetic resonance imaging, and other findings, such as frontotemporal structural and functional abnormalities and cognitive impairments, may converge neurochemically to cause psychosis through aberrant salience and lead to a diagnosis of schizophrenia. The hypothesis has one major implication for treatment approaches. Current treatments are acting downstream of the critical neurotransmitter abnormality. Future drug development and research into etiopathogenesis should focus on identifying and manipulating the upstream factors that converge on the dopaminergic funnel point.

2,311 citations

Journal ArticleDOI
TL;DR: It is found that the dopamine neurons of sensitized animals have become increasingly sensitive to excitatory pharmacological and environmental stimuli or desensitized to inhibitory regulation, and changes in cellular activity or protein synthesis may result in a change in the presynaptic regulation of axon terminal dopamine release.

2,042 citations

Journal ArticleDOI
TL;DR: The findings suggest that ketamine may disrupt dopaminergic neurotransmission in the PFC as well as cognitive functions associated with this region, in part, by increasing the release of glutamate, thereby stimulating postsynaptic non-NMDA glutamate receptors.
Abstract: Subanesthetic doses of ketamine, a noncompetitive NMDA receptor antagonist, impair prefrontal cortex (PFC) function in the rat and produce symptoms in humans similar to those observed in schizophrenia and dissociative states, including impaired performance of frontal lobe-sensitive tests. Several lines of evidence suggest that ketamine may impair PFC function in part by interacting with dopamine neurotransmission in this region. This study sought to determine the mechanism by which ketamine may disrupt dopaminergic neurotransmission in, and cognitive functions associated with, the PFC. A thorough dose-response study using microdialysis in conscious rats indicated that low doses of ketamine (10, 20, and 30 mg/kg) increase glutamate outflow in the PFC, suggesting that at these doses ketamine may increase glutamatergic neurotransmission in the PFC at non-NMDA glutamate receptors. An anesthetic dose of ketamine (200 mg/kg) decreased, and an intermediate dose of 50 mg/kg did not affect, glutamate levels. Ketamine, at 30 mg/kg, also increased the release of dopamine in the PFC. This increase was blocked by intra-PFC application of the AMPA/kainate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione CNQX. Furthermore, ketamine-induced activation of dopamine release and impairment of spatial delayed alternation in the rodent, a PFC-sensitive cognitive task, was ameliorated by systemic pretreatment with AMPA/kainate receptor antagonist LY293558. These findings suggest that ketamine may disrupt dopaminergic neurotransmission in the PFC as well as cognitive functions associated with this region, in part, by increasing the release of glutamate, thereby stimulating postsynaptic non-NMDA glutamate receptors.

1,697 citations

Journal ArticleDOI
TL;DR: The neuro-anatomical and neurochemical substrates subserving inhibitory control and motivational processes in the rodent and primate brain and their putative impact on drug seeking are considered and an integrative hypothesis for compulsive reward-seeking in drug abuse is presented.
Abstract: Drug abuse and dependence define behavioral states involving increased allocation of behavior towards drug seeking and taking at the expense of more appropriate behavioral patterns. As such, addiction can be viewed as increased control of behavior by the desired drug (due to its unconditioned, rewarding properties). It is also clear that drug-associated (conditioned) stimuli acquire heightened abilities to control behaviors. These phenomena have been linked with dopamine function within the ventral striatum and amygdala and have been described specifically in terms of motivational and incentive learning processes. New data are emerging that suggest that regions of the frontal cortex involved in inhibitory response control are directly affected by long-term exposure to drugs of abuse. The result of chronic drug use may be frontal cortical cognitive dysfunction, resulting in an inability to inhibit inappropriate unconditioned or conditioned responses elicited by drugs, by related stimuli or by internal drive states. Drug-seeking behavior may thus be due to two related phenomena: (1) augmented incentive motivational qualities of the drug and associated stimuli (due to limbic/amygdalar dysfunction) and (2) impaired inhibitory control (due to frontal cortical dysfunction). In this review, we consider the neuro-anatomical and neurochemical substrates subserving inhibitory control and motivational processes in the rodent and primate brain and their putative impact on drug seeking. The evidence for cognitive impulsivity in drug abuse associated with dysfunction of the frontostriatal system will be discussed, and an integrative hypothesis for compulsive reward-seeking in drug abuse will be presented.

1,516 citations