Single Dose Of Cocaine Research Articles

Cocaine-induced loss of LTD and social impairments are restored by fatty acid amide hydrolase inhibition

A single dose of cocaine abolishes endocannabinoid-mediated long-term depression (eCB-LTD) in the nucleus accumbens (NAc) within 24 h of administration. However, it is uncertain whether this altered neuroplasticity entails a behavioral deficit. As previously reported, after a single dose of cocaine (20 mg/kg), mice displayed impaired eCB-LTD in the NAc. Such cocaine-induced neuroplastic impairment was accompanied by an altered preference for saccharin and social interactions and a reduction in mRNA levels of the anandamide-catabolizing enzyme NAPE-PLD. The pharmacological increase of anandamide through the fatty acid amide hydrolase (FAAH) inhibitor URB597 (1 mg/kg) reversed the cocaine-induced loss of eCB-LTD in the NAc and restored normal social interaction in cocaine-exposed mice, but it did not affect saccharin preference. Overall, this research underlines the neuroplastic and behavioral alterations occurring after the initial use of cocaine and suggests a potential role for anandamide.

SCH23390 and a humanized anti-cocaine mAb decrease the latency to cocaine-induced reinstatement of lever pressing behavior in rats that self-administer cocaine

In rats that self-administer cocaine, the latency to the reinstatement of lever pressing behavior induced by a single dose of cocaine is due to the time taken for cocaine levels to fall to the satiety threshold. The D1 dopamine receptor antagonist SCH23390, and the recombinant humanized anti-cocaine mAb h2E2 increase the cocaine satiety threshold and would be expected to alter the latency to reinstatement. Male rats acquired cocaine self-administration behavior on an FR1 schedule. These rats received a single injection of cocaine (12 µmol/kg i.v.) after an i.v. injection of SCH23390 or an infusion of h2E2 or vehicle. The latency to, and the duration of, lever pressing was measured but the presses had no consequence. SCH23390 decreased the latency to lever pressing consistent with dose-dependent increases in satiety threshold. The duration of lever pressing behavior was inversely proportional to the SCH23390 dose suggesting that SCH23390 also increased the cocaine compulsion zone. The mAb h2E2 also produced a similar decrease in latency to responding that gradually reversed over 2 weeks. SCH23390 and h2E2 had an additive effect on the decreased latency to cocaine-induced lever pressing. The single cocaine dose reinstatement paradigm within the context of the compulsion zone theory is a useful pharmacological bioassay system to explore potential pharmacotherapies for relapse prevention in cocaine use disorder.

The cocaine compulsion zone theory explains the reinstatement of lever pressing behavior in rats in response to a single cocaine dose

A single non-contingent dose of cocaine reinstates extinguished lever pressing behavior in rats trained to self-administer cocaine. This represents a model of relapse in cocaine use disorder and the number of lever presses has been the standard measure. Lever pressing behavior during self-administration occurs only when cocaine levels are below the satiety threshold and above the remission/priming threshold, a range termed the compulsion zone. Calculated cocaine levels at the time of each lever press during an FR1 self-administration session and following a single non-contingent dose of cocaine were compared. The mean latency to lever pressing behavior was dose dependent and ranged from 1 to 11 min after cocaine doses of 2 or 12 μmol/kg, respectively. This is consistent with higher cocaine doses producing levels above satiety threshold that take more time to fall back to that threshold. The level of cocaine when lever pressing occurred was similar whether cocaine was self-administered or after a single dose of cocaine. The number of lever presses after a single cocaine dose was variable and poorly dose dependent. The latency to the start of lever pressing behavior is a more reliable dependent measure than the number of lever presses. In addition, lever pressing behavior occurs only when cocaine levels are within the compulsion zone. The compulsion zone theory not only explains maintained cocaine self-administration behavior, but also explains the reinstatement of lever pressing behavior in response to a single non-contingent cocaine dose.

Effects of acid-sensing ion channel-1A (ASIC1A) on cocaine-induced synaptic adaptations.

Chronic drug abuse is thought to induce synaptic changes in nucleus accumbens medium spiny neurons (MSNs) that promote subsequent craving and drug-seeking behavior. Accumulating data suggest acid-sensing ion channels (ASICs) may play a critical role. In drug naïve mice, disrupting the ASIC1A subunit produced a variety of synaptic changes reminiscent of wild-type mice following cocaine withdrawal, including increased AMPAR/NMDAR ratio, increased AMPAR rectification, and increased dendrite spine density. Importantly, these changes in Asic1a -/- mice were normalized by a single dose of cocaine. Here we sought to understand the temporal effects of cocaine exposure in Asic1a -/- mice and the cellular site of ASIC1A action. Six hours after cocaine exposure, there was no effect. However, 15h, 24h and 4days after cocaine exposure there was a significant reduction in AMPAR/NMDAR ratio in Asic1a -/- mice. Within 7days the AMPAR/NMDAR ratio had returned to baseline levels. Cocaine-evoked changes in AMPAR rectification and dendritic spine density followed a similar time course with significant reductions in rectification and dendritic spines 24h after cocaine exposure in Asic1a -/- mice. To test the cellular site of ASIC1A action on these responses, we disrupted ASIC1A specifically in a subpopulation of MSNs. We found that effects of ASIC1A disruption were cell autonomous and restricted to neurons in which the channels are disrupted. We further tested whether ASIC1A disruption differentially affects MSNs subtypes and found AMPAR/NMDAR ratio was elevated in dopamine receptor 1-expressing MSNs, suggesting a preferential effect for these cells. Finally, we tested if protein synthesis was involved in synaptic adaptations that occurred after ASIC1A disruption, and found the protein synthesis inhibitor anisomycin normalized AMPAR-rectification and AMPAR/NMDAR ratio in drug-naïve Asic1a -/- mice to control levels, observed in wild-type mice. Together, these results provide valuable mechanistic insight into the effects of ASICs on synaptic plasticity and drug-induced effects and raise the possibility that ASIC1A might be therapeutically manipulated to oppose drug-induced synaptic changes and behavior.

A single dose of cocaine raises SV2A density in hippocampus of adolescent rats.

Cocaine is a highly addictive psychostimulant that affects synaptic activity with structural and functional adaptations of neurons. The transmembrane synaptic vesicle glycoprotein 2A (SV2A) of pre-synaptic vesicles is commonly used to measure synaptic density, as a novel approach to the detection of synaptic changes. We do not know if a single dose of cocaine suffices to affect pre-synaptic SV2A density, especially during adolescence when synapses undergo intense maturation. Here, we explored potential changes of pre-synaptic SV2A density in target brain areas associated with the cocaine-induced boost of dopaminergic neurotransmission, specifically testing if the effects would last after the return of dopamine levels to baseline. We administered cocaine (20 mg/kg i.p.) or saline to rats in early adolescence, tested their activity levels and removed the brains 1 hour and 7 days after injection. To evaluate immediate and lasting effects, we did autoradiography with [3H]UCB-J, a specific tracer for SV2A, in medial prefrontal cortex, striatum, nucleus accumbens, amygdala, and dorsal and ventral areas of hippocampus. We also measured the striatal binding of [3H]GBR-12935 to test cocaine's occupancy of the dopamine transporter at both times of study. We found a significant increase of [3H]UCB-J binding in the dorsal and ventral sections of hippocampus 7 days after the cocaine administration compared to saline-injected rats, but no differences 1 hour after the injection. The [3H]GBR-12935 binding remained unchanged at both times. Cocaine provoked lasting changes of hippocampal synaptic SV2A density after a single exposure during adolescence.

An extended amygdala-midbrain circuit controlling cocaine withdrawal-induced anxiety and reinstatement.

SUMMARYAlthough midbrain dopamine (DA) circuits are central to motivated behaviors, our knowledge of how experience modifies these circuits to facilitate subsequent behavioral adaptations is limited. Here we demonstrate the selective role of a ventral tegmental area DA projection to the amygdala (VTADA→amygdala) for cocaine-induced anxiety but not cocaine reward or sensitization. Our rabies virus-mediated circuit mapping approach reveals a persistent elevation in spontaneous and task-related activity of inhibitory GABAergic cells from the bed nucleus of the stria terminalis (BNST) and downstream VTADA→amygdala cells that can be detected even after a single cocaine exposure. Activity in BNSTGABA→midbrain cells is related to cocaine-induced anxiety but not reward or sensitization, and silencing this projection prevents development of anxiety during protracted withdrawal after cocaine administration. Finally, we observe that VTADA→amygdala cells are strongly activated after a challenge exposure to cocaine and that activity in these cells is necessary and sufficient for reinstatement of cocaine place preference.

The Single Dose Cocaine Reinstatement of Lever‐Pressing Behavior in Rats is Explained by The Compulsion Zone Theory

The compulsion zone theory of the cocaine self‐administration paradigm states that lever‐pressing behavior is induced when cocaine levels fall to or below the satiety threshold. Single injections of cocaine are known to reinstate lever‐pressing in rats trained to self‐administer cocaine. We investigated whether this phenomenon can be explained by the compulsion zone theory. Male Sprague‐Dawley rats (n = 5) were trained to self‐administer cocaine i.v. on an FR‐1 schedule. Once trained, these rats were administered a single dose of cocaine (2 – 12 µmol/kg, i.v.) in four daily sessions per week, and the time to lever‐pressing, the number of presses and the duration of pressing were recorded. The latency from the start of an injection to the resumption of lever pressing increased with the cocaine dose and ranged from approximately 2 min at 2 µmol/kg to more than 15 min at 12 µmol/kg. The D1 dopamine receptor antagonist SCH23390 (10‐30 nmol/kg i.v.) decreased the latency to reinstatement of lever pressing, following a dose of 12 µmol/kg cocaine. The increasing latency to lever‐pressing is consistent with the increasingly higher cocaine levels taking longer to fall to the satiety threshold, while the lower doses are immediately within the compulsion zone. An antagonist‐induced elevation of the satiety threshold explains the reduced latency to reinstatement. The number and duration of lever presses may reflect the time that the cocaine levels are within the compulsion zone. The cocaine satiety threshold model explains the dose‐dependent delay in reinstatement of lever‐pressing behavior and the effect of dopamine antagonists.

Single Low Dose of Cocaine-Structural Brain Injury Without Metabolic and Behavioral Changes.

Chronic cocaine use has been shown to lead to neurotoxicity in rodents and humans, being associated with high morbidity and mortality rates. However, recreational use, which may lead to addictive behavior, is often neglected. This occurs, in part, due to the belief that exposure to low doses of cocaine comes with no brain damage risk. Cocaine addicts have shown glucose metabolism changes related to dopamine brain activity and reduced volume of striatal gray matter. This work aims to evaluate the morphological brain changes underlying metabolic and locomotor behavioral outcome, in response to a single low dose of cocaine in a pre-clinical study. In this context, a Balb-c mouse model has been chosen, and animals were injected with a single dose of cocaine (0.5 mg/kg). Control animals were injected with saline. A behavioral test, positron emission tomography (PET) imaging, and anatomopathological studies were conducted with this low dose of cocaine, to study functional, metabolic, and morphological brain changes, respectively. Animals exposed to this cocaine dose showed similar open field activity and brain metabolic activity as compared with controls. However, histological analysis showed alterations in the prefrontal cortex and hippocampus of mice exposed to cocaine. For the first time, it has been demonstrated that a single low dose of cocaine, which can cause no locomotor behavioral and brain metabolic changes, can induce structural damage. These brain changes must always be considered regardless of the dosage used. It is essential to alert the population even against the consumption of low doses of cocaine.

Accelerated development of cocaine-associated dopamine transients and cocaine use vulnerability following traumatic stress.

Post-traumatic stress disorder and cocaine use disorder are highly co-morbid psychiatric conditions. The onset of post-traumatic stress disorder generally occurs prior to the development of cocaine use disorder, and thus it appears that the development of post-traumatic stress disorder drives cocaine use vulnerability. We recently characterized a rat model of post-traumatic stress disorder with segregation of rats as susceptible and resilient based on anxiety-like behavior in the elevated plus maze and context avoidance. We paired this model with in vivo fast scan cyclic voltammetry in freely moving rats to test for differences in dopamine signaling in the nucleus accumbens core at baseline, in response to a single dose of cocaine, and in response to cocaine-paired cues. Further, we examined differences in the acquisition of cocaine self-administration across groups. Results indicate that susceptibility to traumatic stress is associated with alterations in phasic dopamine signaling architecture that increase the rate at which dopamine signals entrain to cocaine-associated cues and increasethe magnitude of persistent cue-evoked dopamine signals following training. These changes in phasic dopamine signaling correspond with increases in the rate at which susceptible rats develop excessive cocaine-taking behavior. Together, our studies demonstrate that susceptibility to traumatic stress is associated with a cocaine use-vulnerable phenotype and suggests that differences in phasic dopamine signaling architecture may contribute to the process by which this vulnerability occurs.

Forensic Drug Profile: Cocaethylene.

This article is intended as a brief review or primer about cocaethylene (CE), a pharmacologically active substance formed in the body when a person co-ingests ethanol and cocaine. Reference books widely used in forensic toxicology contain scant information about CE, even though this cocaine metabolite is commonly encountered in routine casework. CE and cocaine are equi-effective at blocking the reuptake of dopamine at receptor sites, thus reinforcing the stimulant effects of the neurotransmitter. In some animal species, the LD50 of CE was lower than for cocaine. CE is also considered more toxic to the heart and liver compared with the parent drug cocaine. The plasma elimination half-life of CE is ~2 h compared with ~1 h for cocaine. The concentrations of CE in blood after drinking alcohol and taking cocaine are difficult to predict and will depend on the timing of administration and the amounts of the two precursor drugs ingested. After an acute single dose of cocaine and ethanol, the concentration-time profile of CE runs on a lower level to that of cocaine, although CE is detectable in blood for several hours longer. A strong case can be made for adding together the concentrations of cocaine and CE in forensic blood samples when toxicological results are interpreted in relation to acute intoxication and the risk of an overdose death.

Overexpression of ASIC1A in the nucleus accumbens of rats potentiates cocaine-seeking behavior.

Acid-sensing ion channels (ASICs) are abundantly expressed in the nucleus accumbens core (NAcore), a region of the mesolimbocortical system that has an established role in regulating drug-seeking behavior. Previous work shows that a single dose of cocaine reduced the AMPA-to-NMDA ratio in Asic1a-/- mice, an effect observed after withdrawal in wild-type mice, whereas ASIC1A overexpression in the NAcore of rats decreases cocaine self-administration. However, whether ASIC1A overexpression in the NAcore alters measures of drug-seeking behavior after the self-administration period is unknown. To examine this issue, the ASIC1A subunit was overexpressed in male Sprague-Dawley rats by injecting them with adeno-associated virus, targeted at the NAcore, after completion of 2weeks of cocaine or food self-administration. After 21days of homecage abstinence, rats underwent a cue-/context-driven drug/food-seeking test, followed by extinction training and then drug/food-primed, cued, and cued+drug/food-primed reinstatement tests. The results indicate that ASIC1A overexpression in the NAcore enhanced cue-/context-driven cocaine seeking, cocaine-primed reinstatement, and cued+cocaine-primed reinstatement but had no effect on food-seeking behavior, indicating a selective effect for ASIC1A in the processes underlying extinction and cocaine-seeking behavior.

Initial rewarding effects of cocaine and amphetamine assessed in a day using the single-exposure place preference protocol.

In rodents, only a single dose of cocaine or amphetamine is required to cause a marked increase in extracellular dopamine, induce hyperlocomotion and cause persistent plasticity changes within dopaminergic neurons of the ventral tegmental area (VTA). The initial drug experience is suggested to predict vulnerability of developing addiction, but only few studies have assessed the perception of reward accompanying this initial exposure. We recently presented an approach to assess the initial rewarding effects of cocaine in mice with a single-exposure place preference (sePP) protocol, avoiding repeated drug injections. Here, we demonstrate a condensed version of the sePP, allowing assessment of initial subjective reward-perception within a day. By using this protocol, we demonstrate that a single exposure to both cocaine and amphetamine is sufficient to induce place preference. Furthermore, we use chemogenetics ( Designer Receptors Exclusively Activated by Designer Drugs [DREADD]) to show that both inhibitory and stimulatory modulation of VTA DA signalling disrupts cocaine-induced place preference in the condensed sePP. Our findings support the presence of initial reward-perception of both cocaine and amphetamine, and the formation of drug-context association. In addition, our data support that VTA DA signalling prior to drug exposure affects either reward-perception or the time during which associations are formed, thereby preventing induction of cocaine-induced place preference in the sePP. The easy and timesaving sePP protocol should form a critical basis for further deciphering the complex mechanisms underlying the progression from the initial drug experience to escalating drug intake and addiction.

C-Fos marking of identified midbrain neurons coactive after nicotine administration in-vivo.

Despite the reduced life expectancy and staggering financial burden of medical treatment associated with tobacco smoking, the molecular, cellular, and ensemble adaptations associated with chronic nicotine consumption remain poorly understood. Complex circuitry interconnecting dopaminergic and cholinergic regions of the midbrain and mesopontine tegmentum are critical for nicotine associated reward. Yet our knowledge of the nicotine activation of these regions is incomplete, in part due to their cell type diversity. We performed double immunohistochemistry for the immediate early gene and surrogate activity sensor, c-Fos, and markers for either cholinergic, dopaminergic or GABAergic cell types in mice treated with nicotine. Both acute (0.5 mg/kg) and chronic (0.5 mg/kg/day for 7 days) nicotine strongly activated GABAergic neurons of the interpeduncular nucleus and medial terminal nucleus of the accessory optic tract (MT). Acute but not chronic nicotine also activated small percentages of dopaminergic and other neurons in the ventral tegmental area (VTA) as well as noncholinergic neurons in the pedunculotegmental and laterodorsal tegmental nuclei (PTg/LDTg). Twenty four hours of nicotine withdrawal after chronic nicotine treatment suppressed c-Fos activation in the MT. In comparison to nicotine, a single dose of cocaine caused a similar activation in the PTg/LDTg but not the VTA where GABAergic cells were strongly activated but dopaminergic neurons were not affected. These results indicate the existence of drug of abuse specific ensembles. The loss of ensemble activation in the VTA and PTg/LDTg after chronic nicotine represents a molecular and cellular tolerance which may have implications for the mechanisms underlying nicotine dependence.

A single dose of cocaine enhances prospective memory performance.

Background:Prospective memory is the ability to recall intended actions or events at the right time or in the right context. While cannabis is known to impair prospective memory, the acute effect of cocaine is unknown. In addition, it is not clear whether changes in prospective memory represent specific alterations in memory processing or result from more general effects on cognition that spread across multiple domains such as arousal and attention.Aims:The main objective of the study was, therefore, to determine whether drug-induced changes in prospective memory are memory specific or associated with more general drug-induced changes in attention and arousal.Methods:A placebo-controlled, three-way, cross-over study including 15 regular poly-drug users was set up to test the influence of oral cocaine (300 mg) and vaporised cannabis (300+150 ‘booster’ µg/kg bodyweight) on an event-based prospective memory task. Attentional performance was assessed using a divided attention task and subjective arousal was assessed with the Profile of Mood States questionnaire.Results:Results showed that cocaine enhanced prospective memory, attention and arousal. Mean performance of prospective memory and attention, as well as levels of arousal were lowest during treatment with cannabis as compared with placebo and cocaine as evinced by a significantly increased trend across treatment conditions. Prospective memory performance was only weakly positively associated to measures of attention and arousal.Conclusion:Together, these results indicate that cocaine enhancement of prospective memory performance cannot be fully explained by parallel changes in arousal and attention levels, and is likely to represent a direct change in the neural network underlying prospective memory.

Development of a translational model to screen medications for cocaine use disorder I: Choice between cocaine and food in rhesus monkeys

BackgroundHomologous cocaine self-administration procedures in laboratory animals and humans may facilitate translational research for medications development to treat cocaine dependence. This study, therefore, sought to establish choice between cocaine and an alternative reinforcer in rhesus monkeys responding under a procedure back-translated from previous human studies and homologous to a human laboratory procedure described in a companion paper. MethodsFour rhesus monkeys with chronic indwelling intravenous catheters had access to cocaine injections (0, 0.043, 0.14, or 0.43mg/kg/injection) and food (0, 1, 3, or 10 1g banana-flavored food pellets). During daily 5h sessions, a single cocaine dose and a single food-reinforcer magnitude were available in 10 30-min trials. During the initial “sample” trial, the available cocaine and food reinforcer were delivered non-contingently. During each of the subsequent nine “choice” trials, responding could produce either the cocaine or food reinforcer under an independent concurrent progressive-ratio schedule. ResultsPreference was governed by the cocaine dose and food-reinforcer magnitude, and increasing cocaine doses produced dose-dependent increases in cocaine choice at all food-reinforcer magnitudes. Effects of the candidate medication lisdexamfetamine (0.32–3.2mg/kg/day) were then examined on choice between 0.14mg/kg/injection cocaine and 10 pellets. Under baseline conditions, this reinforcer pair maintained an average of approximately 6 cocaine and 3 food choices. Lisdexamfetamine dose-dependently decreased cocaine choice in all monkeys, but food choice was not significantly altered. ConclusionsThese results support utility of this procedure in rhesus monkeys as one component of a platform for translational research on medications development to treat cocaine use disorder.

Phosphoproteomic analysis of the striatum from pleiotrophin knockout and midkine knockout mice treated with cocaine reveals regulation of oxidative stress-related proteins potentially underlying cocaine-induced neurotoxicity and neurodegeneration

The neurotrophic factors pleiotrophin (PTN) and midkine (MK) are highly upregulated in different brain areas relevant to drug addiction after administrations of different drugs of abuse, including psychostimulants. We have previously demonstrated that PTN and MK modulate amphetamine-induced neurotoxicity and that PTN prevents cocaine-induced cytotoxicity in NG108-15 and PC12 cells. In an effort to dissect the different mechanisms of action triggered by PTN and MK to exert their protective roles against psychostimulant neurotoxicity, we have now used a proteomic approach to study protein phosphorylation, in which we combined phosphoprotein enrichment, by immobilized metal affinity chromatography (IMAC), with two-dimensional gel electrophoresis and mass spectrometry, in order to identify the phosphoproteins regulated in the striatum of PTN knockout, MK knockout and wild type mice treated with a single dose of cocaine (15mg/kg, i.p.). We identified 7 differentially expressed phosphoproteins: 5′(3′)-deoxyribonucleotidase, endoplasmic reticulum resident protein 60 (ERP60), peroxiredoxin-6 (PRDX6), glutamate dehydrogenase 1 (GLUD1), aconitase and two subunits of hemoglobin. Most of these proteins are related to neurodegeneration processes and oxidative stress and their variations specially affect the PTN knockout mice, suggesting a protective role of endogenous PTN against cocaine-induced neural alterations. Further studies are needed to validate these proteins as possible targets against neural alterations induced by cocaine.

Abstracts and Commentaries on Key Articles in the Literature

Abstracts and Commentaries on Key Articles in the Literature

Electroacupuncture Reduces Cocaine-Induced Seizures and Mortality in Mice

The aims of this study were to characterize the protective profile of electroacupuncture (EA) on cocaine-induced seizures and mortality in mice. Mice were treated with EA (2 Hz, 50 Hz, and 100 Hz), or they underwent needle insertion without anesthesia at the Dazhui (GV14) and Baihui (GV20) acupoints before cocaine administration. EA at 50 Hz applied to GV14 and GV20 significantly reduced the seizure severity induced by a single dose of cocaine (75 mg/kg; i.p.). Furthermore, needle insertion into GV14 and GV20 and EA at 2 Hz and 50 Hz at both acupoints significantly reduced the mortality rate induced by a single lethal dose of cocaine (125 mg/kg; i.p.). In the sham control group, EA at 50 Hz applied to bilateral Tianzong (SI11) acupoints had no protective effects against cocaine. In addition, EA at 50 Hz applied to GV14 and GV20 failed to reduce the incidence of seizures and mortality induced by the local anesthetic procaine. In an immunohistochemistry study, EA (50 Hz) pretreatment at GV14 and GV20 decreased cocaine (75 mg/kg; i.p.)-induced c-Fos expression in the paraventricular thalamus. While the dopamine D3 receptor antagonist, SB-277011-A (30 mg/kg; s.c), did not by itself affect cocaine-induced seizure severity, it prevented the effects of EA on cocaine-induced seizures. These results suggest that EA alleviates cocaine-induced seizures and mortality and that the dopamine D3 receptor is involved, at least in part, in the anticonvulsant effects of EA in mice.

Determination of cocaine and its major metabolite benzoylecgonine in rabbit hair by GC/MS

It is important to determine people who use drugs to prevent the use of them. In recent years, hair is routinely used on toxicological analysis as well as biological samples such as blood and urine. The major practical advantages of hair testing are larger detection windows; non-invasive sample collection; easy to transport and store in addition hair analysis can provide a retrospective calendar of an individual's drug use history. In this study, Male New Zealand rabbits (n=10) weighing 2-2,5 kg were used. Two groups were constituted and each group has five rabbits. New Zealand rabbits were intraperitoneally administered with a single dose of cocaine. Following that hair samples were collected during the12th day. According to our data; cocaine is appealed the first five days after single dose of cocaine administration. Benzoylecgonine was not detected after three days. Frequency of benzoylecgonine existence was lower than cocaine. Limit of Detection (LOD) and Limit of Quantification (LOQ) were calculated for cocaine and benzoylecgonine. We did not any significant between groups.

Cocaine enhances ST8SiaII mRNA expression and neural cell adhesion molecule polysialylation in the rat medial prefrontal cortex

The present study investigated whether cocaine (COC) administration evokes changes in the mRNA and protein levels of neural cell adhesion molecule (NCAM) and polysialylated neural cell adhesion molecule (PSA-NCAM) in the medial prefrontal cortex (mPFC) of rats. NCAM/PSA-NCAM is required for neuronal structural plasticity and is constitutively expressed in the mPFC. Rats were treated with a single dose of COC (15 mg/kg, i.p.), and mRNA levels of NCAM and the polysialyltransferases ST8SiaII and ST8SiaIV, enzymes involved in polysialylation of NCAM, were measured at 3, 6 and 24 h after COC treatment. At the same time points, the protein levels of NCAM and PSA-NCAM were measured via western blotting. Acute COC injection did not affect mRNA levels of NCAM and ST8SiaIV, but it increased the mRNA level of ST8SiaII 3 h after injection. At the same time point, an increase in PSA-NCAM, but not in NCAM, protein was observed. Morphological studies of PSA-NCAM protein expression patterns (immunocytochemistry/stereology) performed 3 h after COC administration revealed an enhancement of PSA-NCAM immunostaining in perisomatic-like sites and in the length density of PSA-NCAM-positive neuropil. Double immunofluorescence staining showed that PSA-NCAM perisomatic-like sites surround excitatory neurons. We also observed that a single injection of raclopride (0.4 mg/kg) or SCH 23390 (0.5 mg/kg), D2/D3 and D1 dopamine receptors antagonists, respectively, which were ineffective when given alone, abolished the effects of COC administration on mRNA and protein expression. The data in the present study indicate that COC administration may modify constitutive synaptic plasticity in the mPFC by increasing the NCAM polysialylation in perisomatic innervations of pyramidal neurons via activation of dopamine D1 and D2/D3 receptors.