Rat Model Of Self-administration Research Articles

Nalmefene attenuates reinstatement of methamphetamine-seeking behavior in rats through group II metabotropic glutamate receptors (mGluR2/3)

Nalmefene, an analog to naltrexone, is an antagonist at the μ opioid receptor and a partial agonist at the κ opioid receptor. Both agents are approved for the treatment of alcohol use disorder and opioid addiction. Here, we evaluated the potential of nalmefene for treating psychostimulant dependence using a methamphetamine (METH) self-administration rat model. Rats were trained to press a lever for 0.02-mg intravenous METH infusions paired with drug-associated cues (light and tone) under a fixed ratio 1 schedule. After a 10-day METH self-administration acquisition phase, rats underwent extinction training. A reinstatement test was conducted after fulfilment of the extinction criterion under saline infusions. Re-exposure to METH-associated cues or a priming injection of METH (1.0 mg/kg, i.p.) significantly reinstated METH-seeking behaviors. Pretreatment with nalmefene (10 mg/kg, i.p.) immediately before reinstatement tests significantly attenuated the METH-seeking behaviors induced by both cues and METH priming injection. To investigate the mechanism of effect of nalmefene, we also tested the ability of a group II metabotropic glutamate receptors (mGluR2/3) antagonist, LY341495, to the ameliorating effects of nalmefene. Pretreatment with LY341495 (1.0 mg/kg, i.p.) before nalmefene administration antagonized the effect of nalmefene on reinstatement. LY341495 alone did not affect the reinstatement of lever pressing. We found that nalmefene attenuates METH-seeking behaviors during withdrawal, and this attenuation of reinstatement is mediated by the activation of mGluR2/3. The present findings suggest that nalmefene could decrease incentive motivation for drug use in psychostimulant dependence.

The Cdk5 inhibitor β-butyrolactone impairs reconsolidation of heroin-associated memory in the rat basolateral amygdala.

The persistence of maladaptive heroin-associated memory, which is triggered by drug-related stimuli that remind the individual of the drug's pleasurable and rewarding effects, can impede abstinence efforts. Cyclin-dependent kinase 5 (Cdk5), a neuronal serine/threonine protein kinase that plays a role in multiple neuronal functions, has been demonstrated to be involved in drug addiction and learning and memory. Here, we aimed to investigate the role of cdk5 activity in the basolateral amygdala (BLA) in relapse to heroin seeking, using a self-administration rat model. Male rats underwent 10days of heroin self-administration training, during which an active nose poke resulted in an intravenous infusion of heroin that was accompanied by a cue. The rats then underwent nose poke extinction for 10days, followed by subsequent tests of heroin-seeking behaviour. We found that intra-BLA infusion of β-butyrolactone (100 ng/side), a Cdk5 inhibitor, administered 5 min after reactivation, led to a subsequent decrease in heroin-seeking behaviour. Further experiments demonstrated that the effects of β-butyrolactone are dependent on reactivated memories, temporal-specific and long-lasting on relapse of heroin-associated memory. Results provide suggestive evidence that the activity of Cdk5 in BLA is critical for heroin-associated memory and that the specific inhibitor, β-butyrolactone, may hold potential as a substance for the treatment of heroin abuse.

Animal Experimental Study of the Role of Menthol and Cineole, Two Tobacco Additives, on Nicotine Dependence

To establish a nicotine intravenous self-administration rat model, and to examine, with this model, the effects of two flavoring additives, menthol and cineole, on nicotine dependence. Thirty male Sprague-Dawley (SD) rats were included in the study. After jugular venous catheterization was performed, fixed concentration of nicotine was administered in order to train the rats and establish the rat model of intravenous self-administration groups, receiving intraperitoneal injection of menthol, cineole, and dimethyl sulfoxide (DMSO), the vehicle that was used for the control group. The rats were tested with different fixed-ratio (FR) schedules, including FR1 schedule, in which the rat received one nicotine infusion for every active nose poke, FR2 schedule, in which the rat received one nicotine infusion for every two active nose pokes, and FR5 schedule, in which the rat received one nicotine infusion for every five active nose pokes. The number of active and inactive poke responses and the number of nicotine infusion were documented accordingly. After 10 days of training in nicotine self-administration, the 30 rats demonstrated significant increase in the number of active poke responses and the number of nicotine infusion, which were maintained at a stable and relatively high level. The number of active poke responses was significantly higher that of inactive poke responses ( P< 0.001). The rat model of intravenous nicotine self-administration was successfully established. In the testing phase, under the FR2 schedule, the menthol group showed a reduced number of active poke responses ( P=0.020). Under the FR5 schedule, the groups showed obvious interaction between time and the number of active poke responses ( P<0.011), with the menthol group showing reduced number of active poke responses on day three ( P=0.011) and the cineole group showing rising number of active poke responses on day three ( P=0.003). The DMSO control group did not show any significant change. Menthol and cineole are shown to have an effect on nicotine dependence. When there is relative difficulty involved in obtaining nicotine, menthol suppresses nicotine dependence, whereas cineole enhances nicotine dependence.

Chronic opipramol treatment extinguishes cocaine craving through Rac1 in responders: A rat model study.

Ras-related C3 botulinum toxin substrate 1 (Rac1), of the Rho small GTPase family, is a key regulator of actin cytoskeleton rearrangement and plays an important role in dendritic morphogenesis. Cocaine produces neuronal alterations, including structural changes in dendritic number and morphology. Emerging data indicate sigma-1 receptors (σ-1Rs) as a promising candidate for the prevention of cocaine craving. Opipramol is a σ-1R agonist approved in some European countries for depression and anxiety. Here we report that opipramol, mediated by Rac1, attenuates cocaine-seeking behavior in a rat model of self-administration. The opipramol effect was shown in two phases. It decreased cocaine-seeking behavior throughout the withdrawal phase and, interestingly, showed a significant reduction of cocaine-primed reinstatement in 75% of the opipramol-treated group (termed 'responders'). All opipramol-treated rats showed a decrease in σ-1R mRNA expression levels in the nucleus accumbens (NAc) versus controls. Responders also exhibited significantly decreased NAc Rac1 mRNA expression levels, compared with non-responder rats. Hence, Rac1 differentiated responders from non-responders. Rac1 correlated positively with σ-1R mRNA levels in opipramol responders. In another experiment, Rac1 inhibitor injected directly into the NAc core decreased active lever presses on the first day of extinction, indicating the critical role of Rac1 in the opipramol effect on drug seeking. We postulate that chronic activation of σ-1R, through a dynamic interaction with Rac1, may suggest a new approach to treat substance use disorder (SUD). Rac1 inhibition is a prerequisite for decreasing drug seeking and rehabilitation, and this can be achieved by opipramol, a medication that can be given during detoxification.

P.737 Cocaine alters the gut microbiome in a self-administration rat model: Reversal by dehydroepiandrosterone treatment

Brain–machine interface (BMI) is a useful technology which creates a new way for disable people to communicate with the world, but experimenting with human brains is risky. Hence, a precise mathematical model of the information transmission in the process of limb movement is necessary to be established. In this paper, firstly, we improve the classical single-joint information transmission (SJIT) model through introducing several neuron models, and the improved model is closer to the true single-joint movements. Secondly, a closed-loop system with a Wiener filter-based decoder, an auxiliary controller based on model predictive control (MPC) and a network of Izhikevich neurons is formulated based on the improved model, and the used network of Izhikevich neurons is more time efficient than the existing one. Finally, in this closed-loop system, the intracortical micro-stimulation (ICMS) technology is introduced to feedback the information from the MPC controller in real time. The auxiliary controller assist the brain to control artificial arm by changing the frequency of stimulation current. In this way, the computational complexity of the optimization problem proposed in this paper is greatly reduced, and the closed-loop BMI system designed in this paper can well track the desired trajectory.

Prelimbic cortex is a common brain area activated during cue-induced reinstatement of cocaine and heroin seeking in a polydrug self-administration rat model.

Many preclinical studies examined cue-induced relapse to heroin and cocaine seeking in animal models, but most of these studies examined only one drug at a time. In human addicts, however, polydrug use of cocaine and heroin is common. We used a polydrug self-administration relapse model in rats to determine similarities and differences in brain areas activated during cue-induced reinstatement of heroin and cocaine seeking. We trained rats to lever press for cocaine (1.0mg/kg per infusion, 3-hr/day, 18day) or heroin (0.03mg/kg per infusion) on alternating days (9day for each drug); drug infusions were paired with either intermittent or continuous light cue. Next, the rats underwent extinction training followed by tests for cue-induced reinstatement where they were exposed to either heroin- or cocaine-associated cues. We observed cue-selective reinstatement of drug seeking: the heroin cue selectively reinstated heroin seeking and the cocaine cue selectively reinstated cocaine seeking. We used Fos immunohistochemistry to assess cue-induced neuronal activation in different subregions of the medial prefrontal cortex, dorsal striatum, nucleus accumbens, and amygdala. Fos expression results indicated that only the prelimbic cortex (PL) was activated by both heroin and cocaine cues; in contrast, no significant cue-induced neuronal activation was observed in other brain areas. RNA in situ hybridization indicated that the proportion of glutamatergic and GABAergic markers in PL Fos-expressing cells was similar for the heroin and cocaine cue-activated neurons. Overall, the results indicate that PL may be a common brain area involved in both heroin and cocaine seeking during polydrug use.

Transcriptome profiling of whisker follicles in methamphetamine self-administered rats

Methamphetamine (MA) is a highly addictive psychostimulant that disturbs the central nervous system; therefore, diagnosis of MA addiction is important in clinical and forensic toxicology. In this study, a MA self-administration rat model was used to illustrate the gene expression profiling of the rewarding effect caused by MA. RNA-sequencing was performed to examine changes in gene expression in rat whisker follicles collected before self-administration, after MA self-administration, and after withdrawal sessions. We identified six distinct groups of genes, with statistically significant expression patterns. By constructing the functional association network of these genes and performing the subsequent topological analysis, we identified 43 genes, which have the potential to regulate MA reward and addiction. The gene pathways were then analysed using the Reactome and Knowledgebase for Addiction-Related Gene database, and it was found that genes and pathways associated with Alzheimer’s disease and the heparan sulfate biosynthesis were enriched in MA self-administration rats. The findings suggest that changes of the genes identified in rat whisker follicles may be useful indicators of the rewarding effect of MA. Further studies are needed to provide a comprehensive understanding of MA addiction.

The novel dopamine D3 receptor antagonists/partial agonists CAB2-015 and BAK4-54 inhibit oxycodone-taking and oxycodone-seeking behavior in rats

The use of prescription opioid analgesics, particularly oxycodone, has dramatically increased, and parallels escalated opioid abuse and drug-related deaths worldwide. Understanding the molecular mechanisms underlying the development of opioid dependence and expanding treatment options to counter prescription opioid abuse has become a critical public health matter. In the present study, we first evaluated the reinforcing effects of oxycodone in a rat model of self-administration and then explored the potential utility of two novel high affinity dopamine D3 receptor (D3R) antagonists/partial agonists, CAB2-015 and BAK4-54, for treatment of prescription opioid abuse and dependence. We found that rats acquired oxycodone self-administration rapidly within a range of unit doses that was similar to that for heroin, confirming that oxycodone has significant abuse potential. Strikingly, pretreatment with either CAB2-015 or BAK4-54 (0.4–10 mg/kg, i.p.) dose-dependently decreased oxycodone self-administration, and shifted the oxycodone dose-response curve downward. Repeated pretreatment with CAB2-015 or BAK4-54 (0.4–4 mg/kg) facilitated extinction and inhibited oxycodone-induced reinstatement of drug-seeking behavior. In addition, pretreatment with CAB2-015 or BAK4-54 (4–10 mg/kg) also dose-dependently decreased oxycodone-enhanced locomotor activity, but only CAB2-015 decreased oral sucrose self-administration. These data suggest that D3R antagonists may be suitable alternatives or adjunctive to opioid-based medications currently used clinically in treating opioid addiction and that the D3R-selective ligands (CAB2-015 or BAK4-54) provide new lead molecules for development.

Compulsive methamphetamine taking under punishment is associated with greater cue-induced drug seeking in rats

Methamphetamine (METH) addicts lose control over drug consumption despite suffering multiple adverse medicolegal consequences. To mimic the negative events associated with drug addiction in humans, we recently introduced a rat model of self-administration (SA) with response-contingent punishment on METH intake. These procedures allowed us to distinguish between two addiction-like phenotypes in rats, those that sustained METH taking despite negative consequences (shock-resistant, SR) and rats that significantly reduced their METH intake (shock-sensitive, SS). Here, we further developed our adverse consequence model and examined incubation of METH craving by measuring cue-induced drug seeking in SR and SS rats. Male Sprague–Dawley rats were trained to self-administer METH (0.1mg/kg/injection) or saline intravenously (i.v.) during twenty-two 9-h sessions that consisted of 3 separate 3-h sessions separated by 30min. Subsequently, rats were subjected to incremental footshocks during thirteen additional 9-h METH SA sessions performed in a fashion identical to the training phase. Cue-induced drug craving was then assessed at 2 and 21days after the footshock phase. All rats escalated their intake of METH, with both phenotypes showing similar drug taking patterns during SA training. In addition, rats that continued their METH intake despite negative consequences showed even greater cue-induced drug craving following withdrawal than the rats that reduced METH intake following negative consequences. Taken together, our adverse consequence-based model highlights the possibility of identifying rats by addiction-like phenotypes and subsequent vulnerability to relapse-like behaviors. The use of similar SA models should help in the development of better therapeutic approaches to treat different stages of METH addiction.

Glutamatergic Projections from the Entorhinal Cortex to Dorsal Dentate Gyrus Mediate Context-Induced Reinstatement of Heroin Seeking

Reexposure to the context associated with heroin intake provokes relapse to drug taking after abstinence. The dorsal dentate gyrus (dDG) and entorhinal cortex (EC) have been implicated in contextual memory processing, but the underlying circuit mechanisms in context-induced relapse remain poorly understood. In this study, using a self-administration rat model, we found that activation and synaptic transmission of glutamatergic projections from the EC to the upper blade of dentate gyrus (dDGub) were significantly enhanced during context-induced reinstatement of heroin seeking. This effect was associated with increased of phosphorylation of GluN2B-containing NMDA receptors (GluN2B) at Y1472, ratio of GluN2B membrane/total protein levels, and expression of downstream extracellular signal-regulated kinase-1/2 (ERK1/2) in the dDG region. Furthermore, DREADD-mediated specific inactivation of the EC–dDG pathway or disconnection of the pathway with local postsynaptic GluN2B–ERK1/2 signaling both decreased context-induced reinstatement of heroin seeking. These experimental manipulations had no effect on saccharin-reinforced responding and general locomotor activity in rats. Our results indicate that the EC–dDG pathway mediates context-induced reinstatement of heroin seeking, via the activation of postsynaptic GluN2B–ERK1/2 signaling in the dDG.

Dopamine and glutamate interaction mediates reinstatement of drug-seeking behavior by stimulation of the ventral subiculum.

Background:Drug addiction is a chronic brain disease characterized by recurrent episodes of relapse to drug-seeking/-taking behaviors. The ventral subiculum, the primary output of the hippocampus, plays a critical role in mediating drug-seeking behavior.Methods:A d-amphetamine intravenous self-administration rat model was employed along with focal electrical stimulation of the ventral subiculum (20 Hz/200 pulses) to examine its role in reinstatement of drug-seeking behavior. Dopamine efflux in the nucleus accumbens was measured by in vivo microdialysis and subsequent HPLC-ED analyses. Pharmacological antagonism of dopamine and ionotropic glutamate receptors locally within the nucleus accumbens was employed to assess the role of glutamate and dopamine in reinstatement of drug-seeking behavior induced by stimulation of the ventral subiculum.Results:Here, we demonstrate that reinstatement of drug-seeking behavior following extinction of d-amphetamine self-administration by rats was induced by electrical stimulation in the ventral subiculum but not the cortex. This reinstatement was accompanied by a significant increase in dopamine efflux in the nucleus accumbens and was disrupted by microinfusion of a dopamine D1 or D2 antagonist into the nucleus accumbens. Inhibition of N-methyl-D-aspartate or non- N-methyl-D-aspartate receptors had no effect on the reinstatement induced by ventral subiculum stimulation, whereas co-infusion of D1 and N-methyl-D-aspartate antagonists at formerly ineffective doses prevented drug-seeking behavior.Conclusions:These data support the hypothesis that dopamine/glutamate interactions within the ventral striatum related to memory processes are involved in relapse to addictive behavior.

2Hz-Electroacupuncture Attenuates Conditioned Cue-Evoked Heroin-Seeking Behavior and Increase CB2-Rs Expression in Relapse-Relevant Brain Regions in Heroin-Addicted Rats

In order to investigate the influence of electroacupuncture on heroin seeking behavior and the expression of CB2-Rs in the relapse-relevant brain regions, heroin self-administration rat model which represents the heroin relapse behaviors was developed with progressive fixed ratio program. The model rats were randomly divided into 3 groups: control group, heroin-addicted group and 2Hz electroacupuncture group (stimulating on acupoints zusanli and sanyinjiao). The expression of CB2-Rs in the relapse-relevant brain regions were assessed with immunohistochemistry technologies. The reinstatement of heroin seeking behavior induced by conditioned cue priming showed that compared with the heroin-addicted group, active pokes in the 2Hz electroacupuncture group decreased significantly (p&lt;0.05). Compared with the control group, the expression of CB2-Rs in prefrontal cortex (PFC) and nucleus accumbens (NAc) was significantly decreased (p&lt;0.05) in heroin-addicted group and increaseed significantly recover (p&lt;0.05) in the 2Hz electroacupuncture group. Our present results showed that 2Hz-electroacupuncture could attenuate the conditioned cue-evoked heroin-seeking behavior and the inhibitory effect was mediated partially by the increase CB2-Rs expression in relapse-relevant brain regions in heroin-addicted rats.

P.6.d.003 Acute administration of full 5-HT1B agonist suppresses methamphetamine intake in IV self-administration rat model

Piperazine-related drugs are sold as party pills in the form of tablets, capsules, liquids or powders. These party pills can contain several piperazine derivatives, or even a mixture of piperazines and amphetamine derivatives. This paper describes a screening method using a gas chromatography–mass spectrometry technique allowing the separation and the identification of active components within these mixtures by a combined silylation and acylation derivatization procedure. The studied substances–namely: 1-benzylpiperazine (BZP), 1-(3,4-methylenedioxyben-zyl)piperazine (MDBP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP), 1-(3-chlorophenyl) piperazine (mCPP), 1-(4-methoxyphenyl) piperazine (MeOPP), amphetamine, methamphetamine, ephedrine, pseudoephedrine, 3,4-methylenedioxy-N-methamphetamine (MDMA), 3,4-methylenedi-oxyamphetamine (MDA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA) and N-methyl-1,3-benzodioxolylbutanamine (MBDB)–are separated.

Contribution of Ventral Tegmental GABA Receptors to Cocaine Self-administration in Rats

Recent evidence has suggested that compounds affecting GABAergic transmission may provide useful pharmacological tools for the treatment of cocaine addiction. Using a rat model of self-administration, the present study examined the effects of GABA agonists and antagonists injected directly into the ventral tegmental area (VTA) on cocaine intake in rats trained to self-administer cocaine (0, 125, 250 and 500 microg/infusion) under an FR5 schedule of reinforcement. Separate groups of rats received bilateral intra-VTA injections of the GABA-A antagonist picrotoxin (34 ng/side, n = 7; 68 ng/side, n = 8), GABA-A agonist muscimol (14 ng/side, n = 8), GABA-B agonist baclofen (56 ng/side, n = 7; 100 ng/side, n = 6), picrotoxin (68 ng/side) co-injected with the GABA-B antagonist 2-hydroxysaclofen (100 ng/side, n = 7; 2 microg/side, n = 8) or artificial cerebrospinal fluid (aCSF, n = 6) to assess the effects of the various compounds on the cocaine self-administration dose-response curve. Both picrotoxin and baclofen reduced responding maintained by cocaine, whereas muscimol had no effect on responding. In contrast, neither picrotoxin (n = 6) nor baclofen (n = 8) affected responding maintained by food. Interestingly, 2-hydroxysaclofen effectively blocked the suppression of responding produced by picrotoxin, suggesting that both picrotoxin and baclofen exert their effects via activation of GABA-B receptors. Additionally, these effects appear to be specific to cocaine reinforcement, supporting current investigation of baclofen as a treatment for cocaine addiction.