Characterization of conditioned place preference to cocaine in congenic dopamine transporter knockout female mice

Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.
Psychopharmacology (Impact Factor: 3.88). 08/2005; 180(3):408-13. DOI: 10.1007/s00213-005-2173-y
Source: PubMed


The dopamine transporter (DAT) is thought to play a major role in the rewarding effects of cocaine. Therefore, it is surprising that cocaine reveals conditioned effects in DAT knockout (DAT-KO) mice.
To examine these findings further, we obtained complete dose-effect curves for DAT-KO and DAT wild-type (DAT-WT) mice in a cocaine conditioned place preference (CPP) procedure.
Congenic C57BL6 background female DAT-KO and DAT-WT mice were conditioned in a three-compartment place preference apparatus. Conditioning consisted of three 30-min sessions with cocaine (2.5, 5.0, 10.0, 20.0, or 40.0 mg/kg) and three 30-min sessions with saline. The distribution of time in each choice compartment was determined after each pair of conditioning sessions (one cocaine and one saline session).
DAT-WT mice revealed CPP over a wide range of cocaine doses (5.0-40 mg/kg), whereas DAT-KO mice revealed CPP over a more restricted range of doses, with consistent CPP only occurring with 10 mg/kg of cocaine.
CPP for cocaine develops in both DAT-KO and DAT-WT mice; however, the dose range at which CPP develops is much more restricted in DAT-KO mice than in DAT-WT mice. These observations corroborate the significant role of DAT inhibition in cocaine's conditioned effects.

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    • "up/down regulation of monoamine receptors in response to uptake inhibition, altered concentrations of monoamine metabolites and related molecules) and behavioral levels (e.g. conditioned place preference, locomotor response, drug induced response) [19], [23]–[27]. These genetically altered mice provide rich model systems for assessing differential effects of cocaine on each transporter [15], [19], [28]–[33] and other biological ramifications of the loss of activity of one or more monoamine transporters [14], [17], [20], [22], [34]–[39]. "
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    ABSTRACT: Synaptic levels of the monoamine neurotransmitters dopamine, serotonin, and norepinephrine are modulated by their respective plasma membrane transporters, albeit with a few exceptions. Monoamine transporters remove monoamines from the synaptic cleft and thus influence the degree and duration of signaling. Abnormal concentrations of these neuronal transmitters are implicated in a number of neurological and psychiatric disorders, including addiction, depression, and attention deficit/hyperactivity disorder. This work concentrates on the norepinephrine transporter (NET), using a battery of magnetic resonance imaging techniques and histological correlates to probe the effects of genetic deletion of the norepinephrine transporter on brain metabolism, anatomy and functional connectivity. MRS recorded in the striatum of NET knockout mice indicated a lower concentration of NAA that correlates with histological observations of subtle dysmorphisms in the striatum and internal capsule. As with DAT and SERT knockout mice, we detected minimal structural alterations in NET knockout mice by tensor-based morphometric analysis. In contrast, longitudinal imaging after stereotaxic prefrontal cortical injection of manganese, an established neuronal circuitry tracer, revealed that the reward circuit in the NET knockout mouse is biased toward anterior portions of the brain. This is similar to previous results observed for the dopamine transporter (DAT) knockout mouse, but dissimilar from work with serotonin transporter (SERT) knockout mice where Mn tracings extended to more posterior structures than in wildtype animals. These observations correlate with behavioral studies indicating that SERT knockout mice display anxiety-like phenotypes, while NET knockouts and to a lesser extent DAT knockout mice display antidepressant-like phenotypic features. Thus, the mainly anterior activity detected with manganese-enhanced MRI in the DAT and NET knockout mice is likely indicative of more robust connectivity in the frontal portion of the reward circuit of the DAT and NET knockout mice compared to the SERT knockout mice.
    PLoS ONE 08/2013; 8(3):e57597. DOI:10.1371/journal.pone.0057597 · 3.23 Impact Factor
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    • "To study whether the rewarding properties of cocaine were altered, responses to cocaine (20 mg/kg, i.p.) in a CPP paradigm were studied (Medvedev et al, 2005). Because NR1-KD mice could eventually become sensitized to the locomotor-stimulating effects of cocaine, the development of CPP was studied over time. "
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    ABSTRACT: NMDA receptor-mediated glutamate transmission is required for several forms of neuronal plasticity. Its role in the neuronal responses to addictive drugs is an ongoing subject of investigation. We report here that the acute locomotor-stimulating effect of cocaine is absent in NMDA receptor-deficient mice (NR1-KD). In contrast, their acute responses to amphetamine and to direct dopamine receptor agonists are not significantly altered. The striking attenuation of cocaine's acute effects is not likely explained by alterations in the dopaminergic system of NR1-KD mice, since most parameters of pre- and postsynaptic dopamine function are unchanged. Consistent with the behavioral findings, cocaine induces less c-Fos expression in the striatum of these mice, while amphetamine-induced c-Fos expression is intact. Furthermore, chronic cocaine-induced sensitization and conditioned place preference are attenuated and develop more slowly in mutant animals, but amphetamine's effects are not altered significantly. Our results highlight the importance of NMDA receptor-mediated glutamatergic transmission specifically in cocaine actions, and support a hypothesis that cocaine and amphetamine elicit their effects through differential actions on signaling pathways.
    Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 02/2008; 33(11):2701-14. DOI:10.1038/sj.npp.1301663 · 7.05 Impact Factor
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    • "Fig. 2 shows that cocaine still produced robust CPP in DAT-KD mice. In addition, cocaine produces reward in heterozygous DAT-KO mice [9-11]. These results demonstrate that the reduction of DAT activity and elevated dopaminergic tone does not abolish cocaine's rewarding effect in mice. "
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    ABSTRACT: The dopamine transporter (DAT) plays a critical role in regulating dopamine neurotransmission. Variations in DAT or changes in basal dopaminergic tone have been shown to alter behavior and drug responses. DAT is one of the three known high affinity targets for cocaine, a powerful psychostimulant that produces reward and stimulates locomotor activity in humans and animals. We have shown that cocaine no longer produces reward in knock-in mice with a cocaine insensitive mutant DAT (DAT-CI), suggesting that cocaine inhibition of DAT is critical for its rewarding effect. However, in DAT-CI mice, the mutant DAT has significantly reduced uptake activity resulting in elevated basal dopaminergic tone, which might cause adaptive changes that alter responses to cocaine. Therefore, the objective of this study is to determine how elevated dopaminergic tone affects how mice respond to cocaine. We examined the cocaine induced behavior of DAT knockdown mice that have DAT expression reduced by 90% when compared to the wild type mice. Despite a dramatic reduction of DAT expression and marked elevation in basal dopamine tone, cocaine produced reward, as measured by conditioned place preference, and stimulated locomotor activity in these mice. A reduction in DAT expression and elevation of dopaminergic tone do not lead to adaptive changes that abolish the rewarding and stimulating effects of cocaine. Therefore, the lack of reward to cocaine observed in DAT-CI mice is unlikely to have resulted from the reduced DAT activity but instead is likely due to the inability of cocaine to block the mutated DAT and increase extracellular dopamine. This study supports the conclusion that the blockade of DAT is required for cocaine reward and locomotor stimulation.
    BMC Neuroscience 02/2007; 8(1):42. DOI:10.1186/1471-2202-8-42 · 2.67 Impact Factor
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