Cocaine Conditioned Place Preference Paradigm Research Articles

Endogenous opioid system modulates conditioned cocaine reward in a sex-dependent manner.

Cocaine predictive cues and contexts exert powerful control over behaviour and can incite cocaine seeking and taking. This type of conditioned behaviour is encoded within striatal circuits, and these circuits and behaviours are, in part, regulated by opioid peptides and receptors expressed in striatal medium spiny neurons. We previously showed that augmenting levels of the opioid peptide enkephalin in the striatum facilitates acquisition of cocaine conditioned place preference (CPP), while opioid receptor antagonists attenuate expression of cocaine CPP. However, whether striatal enkephalin is necessary for acquisition of cocaine CPP and maintenance during extinction remains unknown. To address this, we generated mice with a targeted deletion of enkephalin from dopamine D2-receptor expressing medium spiny neurons and tested them in a cocaine CPP paradigm. Low striatal enkephalin levels did not attenuate acquisition of CPP. However, expression of preference, assessed after acute administration of the opioid receptor antagonist naloxone, was blocked in females, regardless of genotype. When saline was paired with the cocaine context during extinction sessions, females, regardless of genotype, extinguished preference faster than males, and this was prevented by naloxone when paired with the cocaine context. We conclude that while striatal enkephalin is not necessary for acquisition, expression, or extinction of cocaine CPP, expression and extinction of cocaine preference in females is mediated by an opioid peptide other than striatal enkephalin. The unique sensitivity of females to opioid antagonists suggests sex should be a consideration when using these compounds in the treatment of cocaine use disorder.

Localizing circuits of cocaine contextual memories

Addiction is characterized by compulsive drug seeking and taking behaviors. Cravings triggered by the presence of environmental cues that were once associated to drug use are a main contributor of relapse and once these drug‐cue memories are formed they are difficult to erase. Addictive drugs like cocaine engage molecular pathways of associate learning, in which recall of an established memory is followed by its reconsolidation, strengthening that memory. The reactivation period is a critical time wherein memories are labile and vulnerable to behavioral and pharmacological interference. Given the widespread negative impact of drug use in our society, it is of great importance to understand the mechanisms underlying drug seeking behaviors to generate effective preventions and treatments. The goal of this study is to elucidate the neural substrate in the nucleus accumbens crucial for the maintenance of cocaine contextual memories, and explore neural plasticity involved. Designer receptors exclusively activated by designer drugs (DREADDs) were used to inhibit neurons at the nucleus accumbens. To accomplish this, adult male mice underwent bilateral intracranial injections of an inhibitory DREADD followed by a cocaine conditioned place preference paradigm. Nucleus accumbens neurons were inhibited via systemic injection of clozapine N‐oxide immediately following reactivation of cocaine contextual memory, and mice were re‐tested for place preference 72 hours and 7 days later. A separate cohort of mice underwent the same cocaine conditioned place preference paradigm, 24 hours post preference testing animals were returned to the cocaine context in a drug‐free state to reactivate cocaine memories. Sixty minutes after, brains were collected and prepared for quantitative RT‐PCR to measure activity‐regulated cytoskeleton‐associate protein (Arc) mRNA. To evaluate the functional plasticity in medium spiny neurons at the nucleus accumbens, upon reconsolidation of cocaine contextual memories, we utilized the fosTRAP2‐Ai14 mouse model. A cohort of male and female fosTRAP2‐Ai14 mice underwent cocaine conditioned place preference exactly as in the previous experiment and brains collected 9 days after recall of cocaine contextual memory and 4‐hydroxytamoxifen induction. Dendritic spine density of fosTRAP cells activated by recall of cocaine context were analyzed. Results show that chemogenetic inhibition of the nucleus accumbens immediately following reactivation of cocaine contextual memory significantly reduced a once established preference for the cocaine context. Furthermore, Arc mRNA expression is upregulated at the nucleus accumbens following exposure to the prior cocaine‐paired context. Finally, we show a significant increase in dendritic spine density in medium spiny neurons at the nucleus accumbens following recall of cocaine context. These findings suggest the nucleus accumbens is important for the reconsolidation of cocaine contextual memories and exhibits dendritic neuroplastic changes upon reconsolidation of cocaine memories.

Retrieval-Driven Hippocampal NPTX2 Plasticity Facilitates the Extinction of Cocaine-Associated Context Memory

BackgroundPostretrieval extinction attenuates the pathological memory associated with psychiatric states such as drug addiction in both humans and rodents. The extinction of a learned response requires gene transcription and protein synthesis after memory retrieval in a time-dependent manner, yet the precise physiological basis after retrieval to allow extinction to neutralize a learned behavior is not fully understood. MethodsIn a cocaine conditioned place preference paradigm, we used a ribosomal tagging strategy to measure the translational state of hippocampal pyramidal neurons after the retrieval of cocaine-associated context memory. Using approaches of electrophysiology, neuronal tracing, and a doxycycline-dependent robust activity marking system, we investigated the cellular and molecular basis of retrieval-induced plasticity that facilitated the extinction. ResultsBioinformatics analysis discovered the specific translational regulation of signaling pathways by retrieval and revealed Nptx2 as the hub gene. Manipulating Nptx2 in dorsal hippocampus bidirectionally regulated the extinction of cocaine-associated context memory as well as the retrieval-driven synaptic remodeling. The pentraxin (PTX) domain of NPTX2 recruited GluA1-AMPA receptors and enhanced the extinction and excitatory synaptic transmission that was prevented by overexpressing carboxyl cytoplasmic tail of GluA1. Furthermore, Nptx2 in retrieval-activated neurons was required for the extinction. ConclusionsThe retrieval-driven upregulation of Nptx2 contributes to the synaptic remodeling in dorsal hippocampus and facilitates the extinction of cocaine-associated context memory, indicating a potential target for the treatment of cue-induced cocaine seeking.

Analyses of cocaine rewarding memories by AAV vector-induced introduction of DREADD system

The development and persistence of drug addiction are associated with the activation and adaptation of the brain reward circuitry, which consists of dopaminergic projection from the ventral tegmental area to the nucleus accumbens (NAc) and the medial prefrontal cortex (mPFC). In cocaine addiction, cocaine-induced activation and neuroplasticity in the brain reward circuitry may contribute to the acquisition and expression of rewarding memory of cocaine, which is critical for the reinstatement of cocaine seeking. However, it remains unclear which neuronal types causally contribute to the retrieval of cocaine-associated rewarding memory. To address this issue, we used DREADD (Designer Receptors Exclusively Activated by Designer Drugs) technology. To selectively suppress mPFC excitatory neurons, we infused an adeno-associated virus (AAV5 or AAV-DJ) vector expressing hM4Di, an inhibitory DREADD, under the control of CaMKII promotor into the mPFC of wildtype mice. To selectively suppress GABAergic neurons, we infused a Cre-dependent AAV (AAV5 or AAV-DJ) vector expressing hM4Di into the mPFC of GAD67-Cre mice or the NAc of vGAT-Cre mice. We found that, in cocaine conditioned place preference paradigm, the activity of mPFC pyramidal and NAc GABAergic neurons is causally related to the retrieval of cocaine-associated memory. The findings suggest that the mPFC-NAc circuit can be a potential therapeutic target for the drug addiction.

Evaluating the Effects of Cholinergic Depletion in the PPTg, LDTg, and VTA on Acoustic Startle Response and Morphine‐Related Reward

Opiate abuse is a worldwide epidemic that costs nations billions of dollars to treat. Rewarding effects of opioids and other drugs of abuse are partially reliant on the activity of dopaminergic neurons located in reward centers of the brain such as the ventral tegmental area (VTA). The VTA receives cholinergic input from only two sources, the pedunculopontine tegmentum (PPTg) and the laterodorsal tegmentum (LDTg). Excitotoxic lesions to the PPTg in rats have previously been shown to reduce the rewarding effect of opiates (Bechara & van der Kooy, 1989; Olmstead & Franklin, 1997; Parker & van der Kooy, 1995). These studies were unable to identify the specific neuronal subtype responsible for the reduced rewarding effect, though they suggested the cholinergic neurons were responsible. By using a diphtheria‐UII fusion toxin to selectively ablate cholinergic neurons in the PPTg and LDTg we were able to test the role of cholinergic projections to the VTA. The toxin was injected bilaterally into the PPTg, LDTg, or VTA of male Sprague‐Dawley rats through stereotaxic surgery. Injection into the VTA creates a retrograde lesion that specifically ablates the cholinergic neurons of the PPTg and LDTg that innervate the VTA.The animals were subjected to an acoustic startle reflex/pre‐pulse inhibition paradigm in weeks 4, 8, and 10 post‐surgery. Animals with cholinergic depletion in the PPTg were unable to startle to the point where pre‐pulse inhibition was unable to be measured. While not significant, there was a trend toward an increase in startle in animals that received a VTA retrograde lesion. These findings suggest that the cholinergic PPTg is necessary for integrating sensory processing and motor output. Cholinergic input to the VTA from both the PPTg and LDTg produced a novel effect. Ten weeks post‐surgery the rats were subjected to a morphine conditioned place preference paradigm (CPP), an extinction period, and then a cocaine CPP paradigm. Animals with lesions to the LDTg were able to form cocaine‐mediated CPP but not morphine‐mediated CPP. PPTg lesioned animals formed preference for both morphine and cocaine. Sham animals and the VTA retrograde animals also formed preference for both drugs. These findings suggest that cholinergic neurons in the LDTg that project to an area that is not the VTA likely play a role in morphine‐related reward, and that the cholinergic output from the PPTg is not required in the formation of morphine conditioned place preference. Taking the results of both experiments together, it can be inferred that the cholinergic LDTg plays a role in reward while the cholinergic PPTg plays a role in sensory processing. It is likely that these two areas work in concert to modulate a variety of behaviors. While these findings don't provide a treatment for opiate abuse, they help to further our understanding of the neuronal mechanisms that drive drug addiction.Support or Funding InformationR00DA024754This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Brief cognitive training interventions in young adulthood promote long-term resilience to drug-seeking behavior

Environmental stress and deprivation increase vulnerability to substance use disorders in humans and promote drug-seeking behavior in animal models. In contrast, experiences of mastery and stability may shape neural circuitry in ways that build resilience to future challenges. Cognitive training offers a potential intervention for reducing vulnerability in the face of environmental stress or deprivation. Here, we test the hypothesis that brief cognitive training can promote long-term resilience to one measure of drug-seeking behavior, cocaine conditioned place preference (CPP), in mice. In young adulthood, mice underwent cognitive training, received rewards while exploring a training arena (i.e. yoked control), or remained in their home cages. Beginning 4 weeks after cessation of training, we conditioned mice in a CPP paradigm and then tested them weekly for CPP maintenance or daily for CPP extinction. We found that a brief 9-day cognitive training protocol reduced maintenance of cocaine CPP when compared to standard housed and yoked conditions. This beneficial effect persisted long after cessation of the training, as mice remained in their home cages for 4 weeks between training and cocaine exposure. When mice were tested for CPP on a daily extinction schedule, we found that all trained and yoked groups that left their home cages to receive rewards in a training arena showed significant extinction of CPP, while mice kept in standard housing for the same period did not extinguish CPP. These data suggest that in early adulthood, deprivation may confer vulnerability to drug-seeking behavior and that brief interventions may promote long-term resilience.

Pharmacological reduction of adult hippocampal neurogenesis modifies functional brain circuits in mice exposed to a cocaine conditioned place preference paradigm.

We investigated the role of adult hippocampal neurogenesis in cocaine-induced conditioned place preference (CPP) behaviour and the functional brain circuitry involved. Adult hippocampal neurogenesis was pharmacologically reduced with temozolomide (TMZ), and mice were tested for cocaine-induced CPP to study c-Fos expression in the hippocampus and in extrahippocampal addiction-related areas. Correlational and multivariate analysis revealed that, under normal conditions, the hippocampus showed widespread functional connectivity with other brain areas and strongly contributed to the functional brain module associated with CPP expression. However, the neurogenesis-reduced mice showed normal CPP acquisition but engaged an alternate brain circuit where the functional connectivity of the dentate gyrus was notably reduced and other areas (the medial prefrontal cortex, accumbens and paraventricular hypothalamic nucleus) were recruited instead of the hippocampus. A second experiment unveiled that mice acquiring the cocaine-induced CPP under neurogenesis-reduced conditions were delayed in extinguishing their drug-seeking behaviour. But if the inhibited neurons were generated after CPP acquisition, extinction was not affected but an enhanced long-term CPP retention was found, suggesting that some roles of the adult-born neurons may differ depending on whether they are generated before or after drug-contextual associations are established. Importantly, cocaine-induced reinstatement of CPP behaviour was increased in the TMZ mice, regardless of the time of neurogenesis inhibition. The results show that adult hippocampal neurogenesis sculpts the addiction-related functional brain circuits, and reduction of the adult-born hippocampal neurons increases cocaine seeking in the CPP model.

A Role for p38 Mitogen-activated Protein Kinase-mediated Threonine 30-dependent Norepinephrine Transporter Regulation in Cocaine Sensitization and Conditioned Place Preference

The noradrenergic and p38 mitogen-activated protein kinase (p38 MAPK) systems are implicated in cocaine-elicited behaviors. Previously, we demonstrated a role for p38 MAPK-mediated norepinephrine transporter (NET) Thr(30) phosphorylation in cocaine-induced NET up-regulation (Mannangatti, P., Arapulisamy, O., Shippenberg, T. S., Ramamoorthy, S., and Jayanthi, L. D. (2011) J. Biol. Chem. 286, 20239-20250). The present study explored the functional interaction between p38 MAPK-mediated NET regulation and cocaine-induced behaviors. In vitro cocaine treatment of mouse prefrontal cortex synaptosomes resulted in enhanced NET function, surface expression, and phosphorylation. Pretreatment with PD169316, a p38 MAPK inhibitor, completely blocked cocaine-mediated NET up-regulation and phosphorylation. In mice, in vivo administration of p38 MAPK inhibitor SB203580 completely blocked cocaine-induced NET up-regulation and p38 MAPK activation in the prefrontal cortex and nucleus accumbens. When tested for cocaine-induced locomotor sensitization and conditioned place preference (CPP), mice receiving SB203580 on cocaine challenge day or on postconditioning test day exhibited significantly reduced cocaine sensitization and CPP. A transactivator of transcription (TAT) peptide strategy was utilized to test the involvement of the NET-Thr(30) motif. In vitro treatment of synaptosomes with TAT-NET-Thr(30) (wild-type peptide) completely blocked cocaine-mediated NET up-regulation and phosphorylation. In vivo administration of TAT-NET-Thr(30) peptide but not TAT-NET-T30A (mutant peptide) completely blocked cocaine-mediated NET up-regulation and phosphorylation. In the cocaine CPP paradigm, mice receiving TAT-NET-Thr(30) but not TAT-NET-T30A on postconditioning test day exhibited significantly reduced cocaine CPP. Following extinction, TAT-NET-Thr(30) when given prior to cocaine challenge significantly reduced reinstatement of cocaine CPP. These results demonstrate that the direct inhibition of p38 MAPK or the manipulation of NET-Thr(30) motif/phosphorylation via a TAT peptide strategy prevents cocaine-induced NET up-regulation, locomotor sensitization, and CPP, suggesting a role for Thr(30)-linked NET regulation in cocaine-elicited behaviors.

Dopamine D1/D5 receptors in the dorsal hippocampus are required for the acquisition and expression of a single trial cocaine-associated memory

The role of the hippocampus in memory supporting associative learning between contexts and unconditioned stimuli is well documented. Hippocampal dopamine neurotransmission modulates synaptic plasticity and memory processing of fear-motivated and spatial learning tasks. Much less is known about the involvement of the hippocampus and its D1/D5 dopamine receptors in the acquisition, consolidation and expression of memories for drug-associated experiences, more particularly, in the processing of single pairing cocaine conditioned place preference (CPP) training. To determine the temporal dynamics of cocaine CPP memory formation, we trained rats in a one-pairing CPP paradigm and tested them at different time intervals after conditioning. The cocaine-associated memory lasted 24h but not 72h. Then, we bilaterally infused the dorsal hippocampus with the GABA A receptor agonist muscimol or the D1/D5 dopamine receptor antagonist SCH 23390 at different stages to evaluate the mechanisms involved in the acquisition, consolidation or expression of cocaine CPP memory. Blockade of D1/D5 dopamine receptors at the moment of training impaired the acquisition of cocaine CPP memories, without having any effect when administered immediately or 12h after training. The expression of cocaine CPP memory was also affected by the administration of SCH 23390 at the moment of the test. Conversely, muscimol impaired the consolidation of cocaine CPP memory only when administered 12h post conditioning. These findings suggests that dopaminergic inputs to the dorsal hippocampus are required for the acquisition and expression of one trial cocaine-associated memory while neural activity of this structure is required for the late consolidation of these types of memories.

Microinjections of a dopamine D1 receptor antagonist into the ventral tegmental area block the expression of cocaine conditioned place preference in rats

Stimulation of dopamine (DA) D1 receptors in the ventral tegmental area (VTA) is involved in primary rewards. In the current study we investigated whether VTA D1 receptor stimulation likewise plays a role in mediating the rewarding effects of cocaine-associated stimuli, using the cocaine conditioned place preference (CPP) paradigm. Rats were prepared with cannulae so as to allow microinjections in the VTA and later conditioned to a cocaine-associated environment using the CPP paradigm. Prior to each conditioning session rats were injected with either saline or cocaine (10mg/kg, intraperitoneally) and then placed in one of the two sides of the CPP apparatus. Sessions lasted 30min a day over a period of eight days, such that rats alternated daily between consistently experiencing cocaine in one side and saline in the other. On the test day, which was conducted one day after conditioning, rats were given bilateral microinjections of one of four doses of the D1 antagonist, SCH 23390, (0, 2, 4 or 8μg/0.5μl) directly into the VTA and allowed free access to both sides of the apparatus. Preference for either side was measured as time spent in each side and compared to the same measures taken before conditioning. The D1 antagonist produced a dose-related, significant reduction in the preference for the cocaine-paired side compared to vehicle. These data suggest that the expression of cocaine conditioned place preference requires stimulation of VTA D1 receptors and, as such, are the first to suggest a role for VTA dendritically released DA in cocaine-, or other reward-, related learning.

Assessing learned associations between conditioned cocaine reward and environmental stimuli in the Wistar Kyoto rat

Clinical studies demonstrate that anxiety disorders increase the risk of substance use disorder. However, few studies have directly assessed anxiety as a vulnerability factor in processing of rewarding stimuli. The Wistar–Kyoto (WKY) rat has been proposed as a model of anxiety vulnerability because it exhibits extreme behavioral inhibition in novel and social environments; yet, it displays paradoxical rapid active avoidance learning that is resistant to extinction. The present study was designed to characterize the acquisition and persistence of cocaine conditioned place preference (CPP) in WKY rats. In the first of a series of three experiments, adult male WKY and Sprague Dawley (SD) rats were given six pairings of cocaine (3, 5, 10, 15mg/kg) or saline on alternating days. SD rats developed cocaine-induced CPP to each of the four doses of cocaine tested. In contrast, WKY rats demonstrated CPP when conditioned with 3, 5, and 10mg/kg, but displayed no preference to the 15mg/kg dose. Next, separate groups of rats were subject to an extended CPP paradigm, which included acquisition, extinction and reinstatement phases. Rats were conditioned with cocaine and saline on alternating days using either a 6/6 (as above) or 4/4 conditioning regimen. Both SD and WKY rats acquired a lasting CPP with the 6/6 conditioning regimen. Results from the 4/4 conditioning regimen show that SD, but not WKY, rats acquired CPP. Preference scores for SD rats during the cocaine primed reinstatement test were significantly different from pretest scores indicating reinstatement of CPP in this group. Paradoxically, WKY rats demonstrated a latent sensitization to the conditioned rewarding effects of cocaine during the drug-primed reinstatement test. Taken together, WKY rats appear to be more sensitive to high doses of cocaine and need more experience with the drug to acquire a preference than SD rats.

The cardiovascular effects of amperozide: interactions with cocaine.

Amperozide is a 5-HT2A receptor antagonist that significantly reduces the acquisition and expression, by rats, of a cocaine conditioned place preference. In order to rule out the possibility that amperozide affects a cocaine conditioned place preference due to effects on blood pressure or heart rate, the cardiovascular effects of amperozide were investigated. Alternating cumulative doses of amperozide (0.5, 1.0, 1.5 and 2.5 mg kg(-1)) or saline and phenylephrine (8 microg kg(-1)) were administered through the femoral vein of awake freely-moving Sprague-Dawley rats and blood pressure and heart rate were recorded from the femoral artery. A single dose of cocaine (5.0 mg kg(-1)) was administered after all the amperozide or saline doses were given. Amperozide (0.5, 1.0, 1.5 and 2.5 mg kg(-1)) did not have any significant effect on blood pressure compared to the saline control treatment to the same animals. However, 0.5 mg kg(-1) amperozide significantly decreased heart rate at 5 and 10 min. after administration. but higher doses did not further depress heart rate. Amperozide did not affect the increased blood pressure and decreased heart rate caused by phenylephrine. an alpha1-adrenoceptor agonist. In addition, amperozide did not affect the cardiovascular response to an intravenous dose of 5.0 mg kg(-1) cocaine. These results suggest that amperozide does not cause direct cardiovascular effects. The mechanism by which the lowest dose of amperozide caused a decrease in heart rate is unknown. Amperozide affects neither alpha-adrenoceptor mediated vasoconstriction nor the increased sympathetic activity caused by the peripheral and central effects of cocaine. The significance of these results, in terms of locomotor activity and the cocaine conditioned place preference paradigm, is discussed.