Prolonged Cocaine Exposure Research Articles

Imaging Dopamine Modulation in Brain Acute Slices for Cocaine Addiction Study with Near-Infrared Carbon Nanotube Sensors

Drug addiction is a pressing issue in modern American society that demands thorough research into its mechanisms. Cocaine locomotor sensitization is a well-established model for understanding the physiological effects of cocaine abuse. Previous studies have established loss of dopamine D2 autoreceptors in striatal tissue as a consequence of locomotor sensitization, yet how these differences in autoreceptor expression affect dopamine signaling remains unclear. Herein, we utilized non-genetically encoded near-infrared fluorescent nanosensors based on carbon nanotubes to image dopamine modulation in live acute coronal brain slices. By leveraging dopamine D2 receptor agonists along with the dopamine nanosensor, we developed a method to identify changes in density of functional D2 autoreceptors and dopamine signaling aberrations that accompany addiction, at the level of individual dopamine synapses. We apply the method to compare changes in D2 autoreceptor activity in the Nucleus Accumbens core in cocaine sensitized and saline (control) mice after prolonged cocaine exposure (5 days). Our preliminarily data indicates the decrease in the number of D2 autoreceptor in cocaine sensitized mice, consistent with the previous studies, and suggests that it leads to higher level of dopamine signaling. Furthermore, we confirm dopamine signaling changes by application of D2 Agonists (quinpirole) are from loss of individual dopamine release sites rather than changes in the quantity of dopamine released, or changes in dopamine reuptake kinetics. Our study provides a route to understand the changes in neuromodulation that underlie the neurobiology of addiction and other dopamine-centric neurological conditions.

Adolescent cocaine differentially impacts psychomotor sensitization and epigenetic profiles in adult male rats with divergent affective phenotypes.

Adolescent drug use reliably predicts increased addiction liability in adulthood, but not all individuals are equally impacted. To explore the biological bases of this differential reactivity to early life drug experience, we used a genetic rat model of temperament and evaluated the impact of adolescent cocaine exposure on adult psychomotor sensitization. Relative to adult bred low-responder (bLR) rats, bred high-responders (bHR) are more sensitive to the psychomotor-activating effects of cocaine and reinstate drug-seeking behavior more readily following prolonged cocaine exposure and/or abstinence. We found that a 7-day sensitizing cocaine regimen (15 mg/kg/day) during either adolescence or adulthood produced psychomotor sensitization in bHRs only, while a dual cocaine exposure prevented further sensitization, suggesting limits on neuroplasticity. By contrast, adolescent cocaine in bLRs shifted their resilient phenotype, rendering them more responsive to cocaine in adulthood following adolescent cocaine. To begin to explore the neural correlates of these behavioral phenotypes, we assessed two functionally opposite epigenetic chromatin modifications implicated in addiction liability, permissive acetylation (ac) and repressive tri-methylation (me3) on Histone 3 Lysine 9 (H3K9), in four striatal sub-regions. In bHRs, decreased H3K9me3 and increased acH3K9 in the nucleus accumbens (NAc) core associated with cocaine sensitization. In bLRs, the combination of cocaine exposure in adolescence and adulthood, which lead to an increased response to a cocaine challenge, also increased acH3K9 in the core. Thus, adolescent cocaine experience interacts with genetic background to elicit different behavioral profiles relevant to addiction in adulthood, with concurrent modifications in the epigenetic histone profiles in the NAc that associate with cocaine sensitization and with metaplasticity.

Genetic background and epigenetic modifications in the core of the nucleus accumbens predict addiction-like behavior in a rat model

This study provides a demonstration in the rat of a clear genetic difference in the propensity for addiction-related behaviors following prolonged cocaine self-administration. It relies on the use of selectively bred high-responder (bHR) and low-responder (bLR) rat lines that differ in several characteristics associated with "temperament," including novelty-induced locomotion and impulsivity. We show that bHR rats exhibit behaviors reminiscent of human addiction, including persistent cocaine-seeking and increased reinstatement of cocaine seeking. To uncover potential underlying mechanisms of this differential vulnerability, we focused on the core of the nucleus accumbens and examined expression and epigenetic regulation of two transcripts previously implicated in bHR/bLR differences: fibroblast growth factor (FGF2) and the dopamine D2 receptor (D2). Relative to bHRs, bLRs had lower FGF2 mRNA levels and increased association of a repressive mark on histones (H3K9me3) at the FGF2 promoter. These differences were apparent under basal conditions and persisted even following prolonged cocaine self-administration. In contrast, bHRs had lower D2 mRNA under basal conditions, with greater association of H3K9me3 at the D2 promoter and these differences were no longer apparent following prolonged cocaine self-administration. Correlational analyses indicate that the association of H3K9me3 at D2 may be a critical substrate underlying the propensity to relapse. These findings suggest that low D2 mRNA levels in the nucleus accumbens core, likely mediated via epigenetic modifications, may render individuals more susceptible to cocaine addiction. In contrast, low FGF2 levels, which appear immutable even following prolonged cocaine exposure, may serve as a protective factor.

Phenotypic mapping of metabolic profiles using self-organizing maps of high-dimensional mass spectrometry data.

A metabolic system is composed of inherently interconnected metabolic precursors, intermediates, and products. The analysis of untargeted metabolomics data has conventionally been performed through the use of comparative statistics or multivariate statistical analysis-based approaches; however, each falls short in representing the related nature of metabolic perturbations. Herein, we describe a complementary method for the analysis of large metabolite inventories using a data-driven approach based upon a self-organizing map algorithm. This workflow allows for the unsupervised clustering, and subsequent prioritization of, correlated features through Gestalt comparisons of metabolic heat maps. We describe this methodology in detail, including a comparison to conventional metabolomics approaches, and demonstrate the application of this method to the analysis of the metabolic repercussions of prolonged cocaine exposure in rat sera profiles.

Intoxication passive à la cocaïne d’un enfant de 25 mois

Cocaine and its principal metabolite were isolated from the urine, confirmed by urine chromatographic analysis, in a 25-month-old girl who had unsteady gait and a third fever seizure. She was premature, had intrauterine growth restriction (IUGR), and a psychomotor delay. The hair examination confirmed prolonged cocaine exposure. The concentration was significant and showed that she had been intoxicated for the 10 previous months. Passive cocaine inhalation may have caused and contributed to these symptoms.

Both High and Low Doses of Cocaine Derail Normal Maternal Caregiving – Lessons from the Laboratory Rat

and maternal aggression (Zimmerberg and Gray, 1992; Johns et al., 1994, 1998; Kinsley et al., 1994). These studies use dosages and treatment regimes of cocaine that model, to some extent, drug use patterns and dosages reported in the dependent human user. Commonly used dosages in these studies result in peak plasma levels of approximately 200–900 ng/ml of cocaine (10–40 mg/kg injected), closely resembling plasma levels reported for the dependent human user, and associated with subjective reports of “feeling high” (Javaid et al., 1978; Smith et al., 1989). Collectively, these studies in rats leave little doubt that plasma levels of cocaine above 200 ng/ml have profound negative effects on all aspects of maternal caregiving, resulting in the complete cessation of all pup-directed behaviors. Once cocaine leaves the blood, most of the components of maternal caregiving return (Zimmerberg and Gray, 1992; Johns et al., 1994, 1998; Kinsley et al., 1994). However, in females subjected to prolonged cocaine exposure during pregnancy, certain effects on postpartum maternal behavioral can be found in the females long after their cocaine treatment has ended. Additionally in offspring, transgenerational effects independent of their exposure to cocaine can be seen (Johns et al., 1994, 2005; McMurray et al., 2008). The profound effects of these doses of cocaine on pup-caregiving by the postpartum female rat underscores the importance of avoiding cocaine if maternal caregiving is to remain intact and to ensure that the normally large allocation of time and energy by the mother in caregiving continues. This leads us to the conclusion that it is crucial to understand the motivational processes at work during choices among stimuli by the postpartum female rats. Even for humans, this may have real world importance as parents care for their offspring in a world full of other choices for their time and attention, including the choice of highly salient stimuli such as cocaine. Both high and low doses of cocaine derail normal maternal caregiving – lessons from the laboratory rat

Estrogen-modulated frontal cortical CaMKII activity and behavioral supersensitization induced by prolonged cocaine treatment in female rats

Females have been demonstrated repeatedly to be more sensitive to cocaine. The role of the frontal cortex (FCX) in mediating behavioral sensitization and the underlying signaling pathways are unclear. The study was designed to characterize the role of FCX calcium/calmodulin-dependent protein kinase II (CaMKII) activity in the behavioral supersensitization observed in female rats after prolonged cocaine exposure. Intact female rats that received cocaine for 9 days followed by 7 days of drug withdrawal constituted the model used for studying the mechanism of supersensitization. This cocaine withdrawal treatment resulted in behavioral supersensitization in intact female rats as indicated by an enhanced behavioral response to cocaine challenge assessed on day 16 (7-day withdrawal) and compared to the response on day 9 of cocaine treatment. This treatment regimen did not lead to supersensitization in male or in ovariectomized (OVX) rats. Administration of estrogen to OVX rats restored behavioral supersensitivity to repeated cocaine. FCX CaMKII activity was significantly altered by cocaine in females, and this effect was related to estrogen's presence; cocaine-induced changes in striatal CaMKII activity were, however, less estrogen-sensitive. Furthermore, estrogen-modulated FCX CaMKII activity in cocaine-supersensitized rats was dependent on D(1) dopamine receptor activation. Estrogen-modulated D(1) dopamine receptor activity mediates the effects of prolonged cocaine exposure on FCX CaMKII, and this, in turn, may contribute to the development of behavioral supersensitivity to repeated cocaine treatment in intact female rats.

Functional effects of cocaine self-administration in primate brain regions regulating cardiovascular function

Cocaine abuse is associated with autonomic dysregulation, such as altered blood pressure and heart rate. Both central and peripheral mechanisms have been implicated in mediating these changes, however, to date, no study has examined functional changes in activity within central autonomic-associated brain regions in response to cocaine in non-human primates. The aim of the present study was to measure local cerebral glucose utilization, in selected autonomic brain regions, in rhesus monkeys that had self-administered cocaine (0.3 mg/kg/infusion) for 5 days (initial) or 100 days (chronic). Measurements were compared with control monkeys, in which responding was maintained by food reinforcement. In general, decreased rates of glucose utilization were observed in targeted areas following both 5 and 100 days of cocaine self-administration compared to control values. However, after initial stages of cocaine exposure, significant reductions in the forebrain were restricted to the bed nucleus of stria terminalis and in the brainstem to the nucleus tractus solitarius and dorsomotor nucleus of the vagus nerve. The pattern of significantly altered functional activity induced by chronic 100-day cocaine self-administration extended within the forebrain to include the paraventricular hypothalamic nucleus, and in the brainstem to include additional autonomic-related nuclei, the nucleus ambiguus and locus coeruleus. These results suggest that even at the initial stages of cocaine self-administration, functional changes in activity occur in autonomic and reward-related brain regions. These alterations progress with prolonged cocaine exposure, and therefore may be involved in mediating changes in central autonomic control and the neuroadaptations reported to result from chronic drug abuse.

Cocaine Upregulates the Dopamine Transporter in Fetal Rhesus Monkey Brain

Cocaine is a highly addictive drug that binds to the dopamine transporter (DAT), inhibits the reuptake of dopamine, and initiates multiple actions within midbrain dopaminergic systems. Using the rhesus monkey, we have investigated the consequences of in utero cocaine exposure on the expression of DAT in the fetal brain. By using the selective DAT ligand [125I]RTI-121 and tyrosine hydroxylase (TH) immunocytochemistry, we found that DAT binding sites are highly developed by day 70 of gestation and show a distribution pattern similar to TH. The rank order of specific 3beta-(4-[125I]iodophenyl)tropane-2beta-carboxylic acid isopropyl ester ([125I]RTI-121) binding densities was substantia nigra-ventral tegmental area > putamen > caudate > lateral hypothalamus > accumbens > linear/interfascicular nuclei >/= globus pallidus > prefrontal cortex. Furthermore, we observed that DAT mRNA was differentially expressed within fetal midbrain dopamine neurons with the highest levels detected in the ventral tier of the substantia nigra pars compacta, and the lowest levels in the ventral tegmental area and the linear/interfascicular nuclei. In utero cocaine exposure between days 22 and 70 significantly increased DAT mRNA expression, and the density of [125I]RTI-121 binding sites within midbrain dopamine neurons in the 70-d-old fetus. This increased DAT expression is accompanied by other presynaptic and postsynaptic neuronal changes, which collectively suggest that midbrain dopamine neurons are hypoactive after prolonged cocaine exposure, a state that may be a contributing factor in the development of attention deficit disorders observed in subjects exposed prenatally to cocaine.

Increased sensitivity to the locomotor depressant effect of a dopamine receptor antagonist during cocaine withdrawal in the rat.

The effect of a dopamine receptor antagonist on locomotor activity was examined during withdrawal from either self-administered or experimenter-administered cocaine. In the self-administration experiment, the locomotor response to a challenge injection of cis-flupenthixol was assessed in photocell cages at 4 h after the cessation of a 12-h cocaine self-administration session. Rats which had self-administered cocaine, and were challenged with cis-flupenthixol (0.05 mg/kg), were found to be hypoactive relative to controls. In the experimenter-administered cocaine experiment, animals were given eight IP injections of 15 mg/kg cocaine over a 9.5-h period, for a total of 120 mg/kg. At 4, 8, and 24 h (tested in three separate groups of rats) after cessation of the eight injections, the locomotor response to a challenge injection of saline or cis-flupenthixol was tested. Cocaine-treated animals displayed a dose-dependent, heightened sensitivity to the locomotor depressant effects of 0.05 mg/kg and 0.2 mg/kg cis-flupenthixol 4 h post-cocaine, whereas they did not show increased sensitivity to 0.05 mg/kg cis-flupenthixol 8 or 24 h post-cocaine. However, cocaine-treated animals displayed a mild hypoactivity 8 h post-cocaine. In a separate group of animals, a dose-response experiment was performed which indicated that a dose of cis-flupenthixol as high as 0.2 mg/kg was required to produce locomotor depression in cocaine-naive rats. The results of this study support clinical observations of dopamine antagonist-precipitated motor dysfunction in abstinent cocaine abusers, and lend further support to the hypothesis that alterations in dopaminergic neurotransmission consequent to prolonged cocaine exposure are partly responsible for some of the symptoms of cocaine withdrawal.

Ovine Fetal-Placental Cocaine Pharmacokinetics During Continuous Cocaine Infusion

To investigate fetal-placental cocaine clearance, and to determine the fetal catecholamine and cardiovascular responses to continuous intravenous cocaine infusion in fetal sheep. Eleven pregnant ewes and their fetuses (127 +/- 2 days' gestation; term 150 days) were chronically instrumented. Fetuses received intravenous cocaine at 0.05, 0.1, or 0.2 mg/kg/minute. Fetal cardiovascular and hematologic measurements were made before and serially for 90 minutes after initiation of the cocaine infusion. Steady-state fetal plasma cocaine concentrations were observed by 15 minutes of infusion and averaged 136 +/- 11, 318 +/- 65, and 610 +/- 36 ng/mL, respectively, at each dose. Fetal-placental cocaine clearance rate was independent of dose (337 +/- 39 mL/kg/minute), indicating that it is a first-order pharmacokinetic process. Fetal plasma concentration of benzoylecgonine, a principle cocaine metabolite, increased throughout the study to approximately 25% above cocaine levels by 90 minutes. There were significant increases in fetal heart rate (from 169 +/- 11 to 242 +/- 36 beats per minute), mean blood pressure (from 53 +/- 4 to 63 +/- 5 mmHg), and systolic blood pressure (from 68 +/- 2 to 80 +/- 5 mmHg), with a corresponding increase in catecholamine levels seen in the fetuses infused with 0.2 mg/kg/minute. These changes were not seen in the fetuses given lower doses of cocaine. Fetal-placental clearance of cocaine is a rapid, first-order pharmacokinetic process. During prolonged cocaine exposure, plasma benzoylecgonine concentrations accumulate significantly. Significant catecholamine and cardiovascular changes are seen in fetal sheep with a continuous infusion of cocaine at 0.2 mg/kg/minute or greater.

Differential effects of short-term or prolonged cocaine exposure on peripheral blood cells in mice

The effects of cocaine on the number of murine peripheral blood cells and on phenotypic expression of lymphocyte subsets were examined using different regimens of drug exposure. Cocaine administered to mice for 7 consecutive days at 1 and 10 mg/kg/day reduced the absolute number of circulating white blood cells and the relative number of cells stained as lymphocytes, polymorphonuclear cells and monocytes. Cocaine did not modify the relative proportion between lymphocytes, polymorphonuclear cells and monocytes. Parallely, there were no changes in the percentage of circulating CD4 + and CD8 + lymphocytes, while the number of natural killer cells increased. In sharp contrast, we didn't observe any significant change in peripheral blood cells after 30 days of consecutive drug administrations.