Browsing by Subject "Cocaine"
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Item The Addicted Phenotype: Protein Phosphorylation Status and Dopamine Receptor Responsiveness(2007-05-22) Edwards, Scott; Self, David W.Up-regulation of cAMP/PKA signaling by drugs of abuse may contribute to escalation and relapse, possibly by differentially altering dopamine receptor-responsiveness in the mesolimbic dopamine system. To investigate this hypothesis, our initial studies measured alterations in cAMP-dependent and -independent protein phosphorylation in vivo produced by chronic cocaine and heroin self-administration, changes in mesolimbic protein phosphorylation compared to individual differences in the propensity for escalating cocaine self-adminstration, and, ultimately, dopamine receptor-mediated regulation of relapse to cocaine seeking in withdrawal. Chronic cocaine self-administration can produce either tolerance or sensitization to certain cocaine-regulated behaviors, but whether differential alterations develop in the biochemical response to cocaine is less clear. In Chapter 2, we studied cocaine-induced phosphorylation of multiple cAMP-dependent and -independent protein substrates in mesolimbic dopamine terminal regions following chronic self-administration. Changes in self-administering rats were compared to changes produced by passive yoked injection to identify regulation related to the context of behavioral reinforcement, whereas acute and chronic yoked groups were compared to identify the development tolerance or sensitization in the biochemical response to cocaine. Microwave-fixed brain tissue was collected immediately following 4 hrs of intravenous cocaine administration, and subjected to western blot analysis of phosphorylated and total protein substrates. Chronic cocaine produced region- and substrate-specific tolerance to cAMP-dependent protein phosphorylation, including phosphorylation of the AMPA GluR1 receptor subunit at serine 845 in striatal and amygdala subregions, and the NMDA NR1 receptor subunit at serine 897 in the CA1 subregion of hippocampus. Tolerance also developed to cAMP-independent GluR1S831 phosphorylation in the prefrontal cortex. In contrast, sensitization to cocaine-induced phosphorylation of the pre-synaptic vesicle protein synapsin I at serine 9 developed in amygdala and hippocampal subregions, while cAMP-dependent phosphorylation of the dopamine-synthesizing enzyme tyrosine hydroxylase at serine 40 decreased in pre-synaptic striatal dopamine terminals in striatal subregions. Cocaine-induced phosphorylation of extracellular signal-regulated kinase (ERK) was dissociated from downstream phosphorylation of the transcription factor cAMP-response element binding protein (CREB) in many brain regions, and failed to develop either tolerance or sensitization with chronic administration, and failed to develop either tolerance or sensitization with chronic administration. Positive reinforcement-related correlations between cocaine intake and protein phosphorylation were found only in self-administering animals, while negative dose-related correlations were found primarily with passive yoked administration. These regional- and substrate-specific adaptations in cocaine-induced protein phosphorylation are discussed in lieu of their potential impact on the development of cocaine addiction. In Chapter 3, we studied alterations in protein kinase A (PKA)-dependent and PKA-independent phosphorylation in multiple brain regions in rats undergoing either spontaneous or naltrexone-precipitated withdrawal (WD) from chronic intravenous heroin self-administration. Spontaneous WD from heroin self-administration produced region-specific increases in PKA-dependent GluR1S845 phosphorylation in the nucleus accumbens shell, basolateral amygdala, hippocampal CA1 and CA3 regions, and premotor cortex after 24 but not 12 hrs, and there were no changes in prefrontal cortex, nucleus accumbens core or caudate-putamen. Increased GluR1S845 phosphorylation occurred earlier (12 hrs) in the central amygdala, ventral tegmental area, and substantia nigra. In contrast, prominent ERK phosphorylation was found in both prefrontal and premotor cortex, CA1 and CA3, caudate-putamen, and basolateral amygdala, but not in nucleus accumbens, or central amygdala in spontaneous WD. Phosphorylation of striatal CREB increased in caudate-putamen but not in nucleus accumbens, paralleling ERK rather than PKA activity in heroin WD. Naltrexone administration potentiated GluR1S845 and ERK phosphorylation in the central amygdala, and ERK phosphorylation in nucleus accumbens core and shell. Thus, spontaneous WD from heroin self-administration produces region- and time-dependent changes in PKA and ERK activity that could contribute to the behavioral manifestation of opiate dependence. In Chapter 4 we studied PKA-dependent GluR1S845 phosphorylation and ERK phosphorylation mediated by ERK kinase in striatal subregions in an animal model of cocaine craving. Here, animals with chronic cocaine self-administration experience were re-exposed to the self-administration test chambers for 1 hr in the absence of cocaine to measure phosphorylation induced by the environmental context paired with cocaine reinforcement. After 1 day WD, GluR1S845 levels were elevated in both self-administering and yoked groups in the nucleus accumbens shell, but this effect persisted only in self-administering animals after 3 weeks WD. In the nucleus accumbens core, context-induced phosphorylation of both GluR1S845 and ERK increased from early to late WD from chronic cocaine self-administration, implicating this region in mediating the intensification of cocaine craving with longer periods of abstinence. These differential region- and substrate-specific adaptations to withdrawal- and context-induced protein phosphorylation could underlie the maintenance of cocaine addiction by exacerbating the potential for drug relapse in withdrawal. Finally, as a behavioral correlate, studies in Chapter 5 sought to compare these changes in protein phosphorylation status with alterations in dopamine-receptor mediated regulation of relapse to cocaine seeking in withdrawal. Here, the cocaine-addicted phenotype was modeled in rats based on individual differences in preferred levels of cocaine intake and a propensity for relapse in withdrawal. Since these cocaine-taking and -seeking behaviors are strongly but differentially regulated by postsynaptic dopamine D1 and D2 receptors in the mesolimbic system, we determined whether the development of cocaine addiction would be related to differential sensitivity in functional D1 and D2 receptor responses. Using a population of 40 outbred Sprague-Dawley rats trained to self-administer cocaine for 3 weeks, we found that animals with higher preferred levels of cocaine intake exhibited a vertical and rightward shift in the self-administration dose-response function, and were more resistant to extinction from cocaine self-administration, similar to phenotypic changes reported in other models of cocaine addiction. After 3 weeks of withdrawal from cocaine self-administration, high intake rats were subsensitive to the ability of the D1 agonist SKF 81297 to inhibit cocaine-seeking behavior, but supersensitive to cocaine seeking triggered by the D2 agonist quinpirole, when compared to low intake rats. Additionally, high intake rats developed profound increases in locomotor responses to D2 receptor challenge from early to late withdrawal times, whereas low intake rats developed increased responsiveness to D1 receptor challenge. In a second experiment, responses to the mixed D1/D2 agonist apomorphine and the NMDA glutamate receptor antagonist MK-801 failed to differ between low and high intake rats. These findings suggest that cocaine addiction is specifically related to differential alterations in functional D1 and D2 receptors that mediate opposing influences on cocaine-seeking behavior. Alterations in dopamine receptor signaling may issue from an enduring up-regulation of cAMP/PKA signaling in drug withdrawal. The potential for reduced D1 receptor (Gs/Golf-coupled) sensitivity to account for tolerance to cocaine-regulated PKA-dependent protein phosphorylation during self-administration (Chapter 2) is discussed in Chapter 6. Conversely, it is possible that PKA up-regulation in cocaine WD (Chapter 4) could account for the paradoxical sensitization of subsequent Gi/Go-coupled D2 receptor responses. Thus, addiction-related alterations in D1 and D2 dopamine receptor responses may ultimately involve complex reciprocal interactions between adaptations in PKA signaling pathways that differentially influence D1 and D2 receptor signaling.Item The cardiovascular complications of cocaine use(1990-06-28) Lange, Richard A.Item Characterization of Histone Deacetylase 4 and Histone Deacetylase 5 in Cocaine-Related Behaviors(2016-04-15) Carreira Franceschi, Maria Beatriz; Self, David W.; Cowan, Christopher W.; Huber, Kimberly M.; Rothenfluh, AdrianIn recent years a focus on epigenetic mechanisms as mediators of cocaine-related behavioral, structural and functional plasticity has developed. One family of epigenetic molecules that may underlie cocaine behavioral and functional changes is the histone deacetylase family that acts to mediate transcriptional repression. The class IIa subgroup of histone deacetylases is poised as an intracellular signal detector and effector by virtue of their ability to shuttle subcellularly in a dynamic and activity-dependent manner primarily driven by phosphorylation status of the protein at multiple residues. The overlying goal of this thesis was to two-faceted: to characterize the regulation of two class IIa members, HDAC4 and HDAC5, by cocaine-mediated signaling and to characterize the role of HDAC4 and HDAC5 in cocaine-associated behavioral plasticity. We report the regulation of phosphorylation and localization of HDAC4 and HDAC5 is in opposition. HDAC5 is dephosphorylated and accumulated in the nuclear compartment in response to cocaine, dopamine dependent signaling and cAMP activity. Meanwhile, we observe that HDAC4 is weakly dephosphorylated by cAMP activity in culture but weakly phosphorylated in vivo. These findings encouraged the analysis of function of these highly homologous class members. We assessed the function of HDAC4 and HDAC5 in the nucleus accumbens, a critical region for reward, by over-expressing wildtype and nuclear variants by targeted viral-mediated gene transfer. We report an attenuation of cocaine reward learning by nuclear HDAC5 but not wildtype or HDAC4 over-expression. We further analyzed the role of HDAC5 in self-administration behavior and report an effect of nuclear HDAC5, but not wildtype, on models of reinstatement of seeking, a preclinical model of relapse. These effects were observed in the absence of an effect on intake, sensitivity or motivation to self-administer. Because HDAC4 and HDAC5 bind nuclear transcriptional regulators to exert transcriptional repression of target genes we analyzed the dependence of nuclear HDAC5 on interacting with MEF2, a primary binding partners, and report that this interaction is likely required for modulating reinstatement of seeking but dispensable for cocaine reward. Taken together, these findings highlight the role of nuclear HDAC5 but not HDAC4 to limit cocaine reward and aspects of cocaine addiction-like behavior.Item Cocaine Use and General Anesthesia: A Prospective Study of Cardiovascular Effects(2018-01-23) Vu, Kevin; Kim, Agnes; Lu, Rachael; Sharifi, Eve; Moon, Tiffany SunBACKGROUND: Cocaine usage in surgical patients is a concern for many hospitals. In large urban hospitals, up to 1.0% of elective surgical patients and 38% of major trauma victims may test positive for cocaine preoperatively. Previous retrospective studies have shown that cocaine positive surgical patients do NOT have an increase in adverse hemodynamic events, length of stay, or mortality compared to cocaine negative controls. However, prospective studies evaluating the impact of recent cocaine use on intraoperative hemodynamics plus inflammatory and cardiac biomarkers have not been undertaken. HYPOTHESIS: This study will test the hypothesis that patients who have 1) a preoperative toxicity screen that demonstrates recent cocaine use, are 2) undergoing non-emergent surgery with general anesthesia, and 3) have normal vital signs will NOT experience an increased incidence of adverse perioperative cardiovascular events compared to similar control patients with a negative toxicity screen. METHODS: This prospective study stratifies patients into cocaine positive and cocaine negative cohorts. Cocaine positive patients were non-toxic with positive urine toxicology, while cocaine negative patients were defined as having used cocaine in the past year with negative urine toxicology. Anesthesia protocol was standardized. The primary outcomes measured were intraoperative hemodynamics and vasoactive medications, with a secondary outcome of pre- vs. post-operative troponin levels. DATA: Preliminary outcome analysis of cocaine positive (N = 59) and cocaine negative patients (N = 40) are shown in the table below: Primary Hemodynamic Outcomes as Percentage of Anesthesia Duration Hemodynamic Events Cocaine Negative Cocaine Positive MAP <55 or >110 mmHG 1.8 1.4 HR <50 or >100 BPM 3.2 2.7 Perioperative Change in Troponin T No Change 95.0% 100.0% Decrease 2.5% 0.0% Increase 2.5% 0.0% CONCLUSION: The data supports the idea that positive cocaine urine toxicology tests in non-toxic individuals are not associated with increased cardiovascular instability or troponin elevation. Thus, automatic cancellation of these patients may not be warranted. Further analysis of the full study cohort (N = 300) will be completed at the end of 2017.Item [News](1989-02-01) Harrell, AnnItem Pathophysiology and management of cocaine-related myocardial ischemia and infarction(1994-07-21) Hillis, L. DavidItem The Role of Cdk5 in the Regulation of Dopamine Neurotransmission, Neuronal Excitability, and Reward-Related Behavior(2010-05-14) Benavides, David Roger; Bibb, James A.Cyclin-dependent kinase 5 (Cdk5) regulates dopamine neurotransmission and synaptic plasticity and has been implicated as a homeostatic target of chronic psychostimulant exposure. In order to investigate the role of Cdk5 in the modulation of signal transduction pathways that regulate motivation and rewardrelated behavior, we developed several Cre/loxP conditional knock-out systems that allow temporal and spatial control of Cdk5 expression in the adult brain. Loss of Cdk5 in the adult brain increased the psychomotor-activating properties of cocaine and enhanced incentive motivation for food. Behavioral changes were accompanied by increased excitability of medium spiny neurons in the nucleus accumbens (NAc) in conditional Cdk5 knock-out mice. Targeted deletion of Cdk5 in the NAc facilitated cocaine-induced locomotor sensitization and conditioned place preference for cocaine. These results suggest that Cdk5 acts as a negative regulator of neuronal excitability in the NAc and that Cdk5 may govern the behavioral effects of cocaine and motivation for reinforcement. In a candidate search for putative Cdk5 substrates that may regulate dopamine-cAMP dependent kinase (PKA) signaling, we identified, confirmed, and characterized Cdk5-dependent phosphorylation of Thr69 RIIβ. We generated novel phosphorylation state-specific antisera to pThr69 RII-beta and found that pThr69 RII-beta levels were reduced in conditional Cdk5 knock-out mice. Functionally, phosphorylation of Thr69 dramatically enhanced calpain-mediated cleavage of RII-beta in vitro, but did not alter inhibition of PKAcat or cAMP binding. Phosphorylation of Thr69 also increased the interaction of RII-beta with an A-kinase anchoring protein (AKAP) docking motif in vitro. In addition, we generated novel phosphorylation state specific antibodies to regulatory phosphorylation sites on cAMP-specific phosphodiesterase 4 (PDE4), an important modulator of PKA signaling. These antibodies to Ser53 PDE4D3 (PKA site) and pSer573 PDE4D3 (ERK site) provide insight into the crosstalk between PKA and ERK pathways in the regulation of cAMP. Finally, we identified and confirmed Thr292 as the site of Cdk5-dependent phosphorylation of MEK1. In conclusion, Cdk5 likely regulates PKA signaling through numerous pathways, including but not limited to DARPP-32, RII-beta, PDE, and MEK1. In summary, these studies identify novel regulatory mechanisms through which Cdk5 controls PKA signaling as well as the interplay between PKA and ERK signaling pathways that regulate motivation and reward-related behavior.Item [Southwestern News](1999-10-20) Steeves, Susan A.Item [Southwestern News](2003-02-06) Horton, RachelItem [Southwestern News](1994-02-16) Mitchell, SusanItem [Southwestern News](2002-03-05) Shields, AmyItem [Southwestern News](2001-08-02) Shields, AmyItem [UT News](1986-08-22) Rutherford, SusanItem [UT Southwestern Medical Center News](2007-04-02) Hansard, Donna Steph; Morales, KatherineItem [UT Southwestern Medical Center News](2007-08-13) Morales, Katherine