Interaction of noncontingent cocaine and contingent drug-paired stimuli on cocaine reinstatement

Effects of repeated yohimbine administration on reinstatement of palatable food seeking: involvement of dopamine D1 -like receptors and food-associated cues

Acute exposure to the pharmacological stressor yohimbine induces relapse to both food and drug seeking in a rat model. However, no systematic studies on the effects of chronic stress on relapse have been conducted. Because chronic stress causes changes in dopamine D₁ -like receptor-mediated transmission in prefrontal cortex (a relapse node), we tested the hypothesis that chronic exposure to stress increases vulnerability to relapse via dopamine-mediated mechanisms. Additionally, to determine the role of food-conditioned cues in reinstatement of food seeking, we made discrete food-paired cues either available (CS Present) or not available (CS Absent) during extinction and reinstatement testing. Rats responded for palatable food reinforcers in daily 3-hour sessions, and the behavior was extinguished. To model chronic stress, rats were injected daily with yohimbine (0.0, 2.5, or 5.0 mg/kg; i.p.) during the first 7 days of extinction. Injections were combined with SCH-23390 (0.0, 5.0, or 10.0 µg/kg; i.p.), a D₁ -like receptor antagonist. Rats were then tested for reinstatement of food seeking triggered by acute yohimbine (0.0, 1.0, or 2.0 mg/kg; i.p.) and pellet priming. Rats treated previously with chronic yohimbine displayed increased responding following acute yohimbine priming relative to non-chronically stressed rats, but in the CS Absent condition only. Conversely, the lower dose of chronic yohimbine caused an increase in pellet-primed reinstatement, but this effect was more pronounced in the CS Present condition. Importantly, SCH-23390 combined with repeated yohimbine injections attenuated these effects. Thus, chronic stress may increase vulnerability to relapse under specific circumstances via a dopamine D₁ -like receptor-mediated mechanism.

Efficacy of buspirone for attenuating cocaine and methamphetamine reinstatement in rats

BACKGROUND

There are no approved pharmacotherapies for preventing psychomotor stimulant relapse. The operant reinstatement model has been suggested as a screen for identifying candidate medications. The present study examined if the anxiolytic buspirone could attenuate reinstatement of extinguished responding in Long-Evans rats that previously self-administered intravenous cocaine or methamphetamine.

METHODS

Rats were trained in 2-h daily sessions to self-administer 0.5mg/kg cocaine or 0.1mg/kg methamphetamine infusions followed by 12 days of instrumental extinction. Reinstatement was evoked by 17mg/kg i.p. cocaine primes or response-contingent cocaine-paired cues in cocaine-reinforced rats, and by 1mg/kg i.p. methamphetamine primes or response-contingent methamphetamine-paired cues in methamphetamine-reinforced rats.

RESULTS

Buspirone (1 and 3mg/kg) significantly (p<0.05) attenuated cocaine cue but not cocaine prime reinstatement. Buspirone (1 and 3mg/kg) also significantly attenuated methamphetamine cue reinstatement. Buspirone (3mg/kg) significantly attenuated methamphetamine prime reinstatement. During all reinstatement tests, 3mg/kg buspirone reduced levels of inactive lever pressing relative to those of vehicle, significantly so during the cocaine cue-induced reinstatement tests.

CONCLUSIONS

Given the complexity of buspirone's neuropharmacology consisting of serotonin 5-HT1A receptor partial agonist activity, and dopamine D2, D3 and D4 receptor antagonist effects, it is uncertain which of these activities or their combination is responsible for the present results. Overall, these results suggest that buspirone may reduce the likelihood of relapse to cocaine and methamphetamine use under some conditions, although this speculation must be interpreted with caution given buspirone's similar potency to attenuate inactive-lever responding.

The selective dopamine uptake inhibitor, D-84, suppresses cocaine self-administration, but does not occasion cocaine-like levels of generalization

A successful replacement pharmacotherapy for treating cocaine dependency would likely reduce cocaine's abuse, support a low abuse liability, overlap cocaine's subjective effects, and have a long duration of action. Inhibitors with varying selectivity at the dopamine transporter (DAT) have approximated these properties. The objective of the present study was to characterize the behavioural effects of an extremely selective DAT inhibitor, (+) trans-4-(2-Benzhydryloxyethyl)-1-(4-fluorobenzyl) piperadin-3-ol (D-84), a 3-hydroxy substituted piperidine derivative of GBR-12935, for its cocaine-like discriminative stimulus effects, its effects on cocaine self-administration, and for its own self-administration. During cocaine discrimination tests, cocaine occasioned the 10 mg/kg cocaine training stimulus with an ED(50) value of 3.13 (1.54-6.34) mg/kg, and reduced response rates with an ED(50) value of 20.39 (7.24-57.44) mg/kg. D-84 incompletely generalized to the cocaine stimulus occasioning a maximal 76% cocaine-lever responding, while reducing response rates with lower potency than cocaine (ED(50)=30.94 (12.34-77.60) mg/kg). Pretreatment with D-84 (9.6-30.4 mg/kg) significantly (P<0.05) reduced cocaine intake at 17.1 mg/kg D-84 when cocaine was self-administered at 0.5 mg/kg/infusion, and at 30.4 mg/kg D-84 when cocaine was self-administered at 0.1, 0.5 .and 1.0 mg/kg/infusion. During self-administration tests with D-84 (0.1-1 mg/kg/infusion), numbers of infusions significantly exceeded vehicle levels at 0.3 mg/kg/infusion. These results show that D-84 pretreatment can decrease cocaine intake especially when high doses of cocaine are being self-administered. This observation, combined with its incomplete generalization to the cocaine discriminative stimulus and its reported long duration of action, provides a profile consistent with a potential replacement therapy for treating cocaine-abusing patients.

Effectiveness of analogs of the kappa opioid receptor antagonist (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic) to reduce U50,488-induced diuresis and stress-induced cocaine reinstatement in rats

RATIONALE

The kappa opioid receptor (KOR) antagonist, JDTic, was reported to prevent stress-induced reinstatement of cocaine-maintained responding and to have antidepressant-like effects.

OBJECTIVES

Our objectives were to determine whether analogs of JDTic retained KOR antagonist activity and whether an orally effective analog prevented footshock-induced cocaine reinstatement.

METHODS

RTI-194 (i.g. 1-30 mg/kg, s.c. 0.3-10 mg/kg, and i.p. 30 mg/kg), RTI-212 (s.c. 0.3-10 mg/kg and i.p. 30 mg/kg), and RTI-230 (i.g. 3-30 mg/kg and i.p. 1-30 mg/kg) were evaluated for their ability to block diuresis induced by 10-mg/kg U50,488 in rats. RTI-194 was additionally evaluated i.g. (3-100 mg/kg) for its ability to prevent footshock-induced reinstatement of responding previously reinforced with 0.5-mg/kg/inf cocaine.

RESULTS

RTI-194 significantly (p < 0.05) attenuated U50,488-induced diuresis when given i.g., s.c., and i.p. RTI-194s effectiveness increased 1 week following administration. RTI-212 was ineffective. RTI-230 was ineffective when given i.g., but blocked diuresis at 24 h and 8 days (1, 10, and 30 mg/kg), 15 days (10 and 30 mg/kg), 22 and 29 days (30 mg/kg) following i.p. administration. Footshock reinstated responding in vehicle-but not RTI-194 (30 and 100 mg/kg)-treated rats.

CONCLUSIONS

RTI-194 and RTI-230 are effective KOR antagonists, and RTI-194 is now included with JDTic as the only reported compounds capable of antagonizing the KOR following oral administration. The failure of stress to reinstate cocaine seeking in rats treated with RTI-194 is consistent with results reported with JDTic, although it had less efficacy in lowering response levels than JDTic, suggesting a diminished overall effectiveness relative to it.

Mouse model of relapse to the abuse of drugs: procedural considerations and characterizations

To identify genetic risk factors involved in relapse to the abuse of drugs in humans, it is essential for researchers to develop a reliable mouse model of relapse by extending well-established extinction-reinstatement procedures in rats. Because of technical difficulties such as the relatively short duration of catheter patency in mice, few reports are available on the characterization of extinction-reinstatement behavior in wild-type and genetically engineered mutant mice. In this review, efforts are made to describe practical considerations during the establishment of extinction-reinstatement procedure in mice, including drug-primed, cue-induced, and stress-triggered reinstatement of previously extinguished drug-seeking behavior. Next, attention will be given to some characteristics of extinction-reinstatement behavior in mice. The present review might provide a new impetus in the exploration of genetic risk factors involved in relapse to drug dependence/addiction in humans using extinction-reinstatement procedures in widely available mutant mice.

Effect of drug-paired exteroceptive stimulus presentations on methamphetamine reinstatement in rats

The purpose of the present study was to examine the impact of drug-paired cues on methamphetamine reinstatement. Three groups of rats were trained to self-administer 0.1 mg/kg/infusion methamphetamine. Each methamphetamine infusion was accompanied by a 6 s flashing light+tone stimulus (cues). After training, the groups were then given 12, daily extinction sessions either with or without response-contingent drug-paired cues and then tested for 1 mg/kg i.p. methamphetamine priming-induced reinstatement either with or without cues. Methamphetamine priming significantly reinstated drug-appropriate responding regardless of whether response-contingent cues were omitted during both extinction and testing, presented during both extinction and testing, or omitted during extinction but presented during reinstatement testing. The group in which cues were omitted during extinction and presented during reinstatement exhibited significantly greater reinstatement than did the other two groups. A separate group of rats was also tested demonstrating that response-contingent presentation of previously methamphetamine-paired cues alone, without methamphetamine priming, significantly reinstated drug-appropriate responding. These data show that methamphetamine priming produces a robust reinstatement effect which can be influenced by drug-paired cues.

Kappa agonist-induced reinstatement of cocaine seeking in squirrel monkeys: a role for opioid and stress-related mechanisms

Kappa opioid agonists were at one time proposed as candidate pharmacotherapies for cocaine addiction, mainly because of their ability to decrease dopamine neurotransmission and attenuate the behavioral effects of cocaine in laboratory animals. Recent studies, however, suggest that kappa agonists also may mimic and/or enhance some of the effects of cocaine through mechanisms related to stress. The current study used a reinstatement procedure to examine the ability of the kappa agonists spiradoline and enadoline to reinstate extinguished cocaine seeking in squirrel monkeys previously trained to self-administer cocaine under a second-order schedule of i.v. drug injection. Opioid- and stress-related mechanisms were evaluated in antagonism studies with the opioid antagonists naltrexone and nor-binaltorphimine (nor-BNI), the corticotropin-releasing factor receptor antagonist butyl-ethyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo [2,3-d]pyrimidin-4-yl]amine (CP 154,526), and the alpha(2)-adrenoceptor agonist clonidine combined with either spiradoline or enadoline. When tested alone, priming with spiradoline and enadoline induced significant reinstatement of cocaine-seeking behavior to approximately 45% of the maximum reinstatement induced by cocaine. Reinstatement of cocaine seeking induced by intermediate doses of spiradoline was greater in the presence than in the absence of response-contingent presentations of a cocaine-paired stimulus. Spiradoline- and enadoline-induced reinstatement of drug seeking was attenuated by naltrexone but not by nor-BNI. Spiradoline-induced reinstatement of cocaine seeking was also antagonized by CP 154,526 and clonidine. The results point to interactions between a subpopulation of kappa opioid receptors and central corticotropin-releasing factor and noradrenergic stress systems in the reinstatement of cocaine seeking induced by kappa agonists.

Reinstatement of nicotine-conditioned place preference by drug priming: Effects of calcium channel antagonists

Reinstatement of drug-seeking behaviour in animals is relevant to drug relapse in humans. In the present study, we used the conditioned place preference paradigm to investigate the establishment, extinction, reinstatement and cross-reinstatement of nicotine-induced place conditioning in rats. Nicotine produced a place preference to the initially less-preferred compartment paired with its injections during conditioning (0.5 mg/kg, i.p., three drug sessions). Once established, nicotine place preference was extinguished by repeated training. Following this extinction phase, the reinstatement of place conditioning was investigated. For this purpose, nicotine-experienced rats were challenged with nicotine (0.5 mg/kg, i.p.) or morphine (10 mg/kg, i.p.). These priming injections of both drugs renewed a marked preference for the compartment previously paired with nicotine. In the second step, we examined the influence of the calcium channel antagonists, nimodipine (10 and 20 mg/kg, i.p.) and flunarizine (5 and 10 mg/kg, i.p.), on the reinstatement of nicotine-conditioned place preference induced by priming doses of nicotine and morphine. It was shown that the calcium channel blockers dose dependently attenuated the reinstatement of nicotine place preference induced by both drugs. These findings support the hypothesis that similar neural calcium-dependent mechanisms are involved in nicotine- and morphine-induced reinstatement. Finally, the conditioned place preference paradigm appears to be a useful tool for studies of the relapse of drug-seeking behaviour in laboratory animals.

Differential effects of the novel kappa opioid receptor antagonist, JDTic, on reinstatement of cocaine-seeking induced by footshock stressors vs cocaine primes and its antidepressant-like effects in rats

RATIONALE

Stress and depression have been linked to relapse of cocaine abuse. Antagonism of the kappa opioid receptor (KOR) has been reported to attenuate some effects of stressors, and antagonism of the KOR has been reported to have antidepressant-like properties.

OBJECTIVES

Our objective was to determine whether the potent and selective KOR antagonist, (3R)-7-hydroxy-N-{(1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl}-1,2,3,4-tetrahydro-3-isoquinoline-carboxamide (JDTic), can reduce the ability of a stressor (intermittent footshock) to reinstate cocaine-seeking behavior and to have antidepressant-like effects in the forced swim test (FST).

METHODS

Male Long-Evans hooded rats were trained to lever-press, reinforced with 0.5 mg/kg i.v. infusion of cocaine, according to fixed ratio 1 reinforcement schedules during daily 2-h experimental sessions. After performance had stabilized, lever pressing was extinguished for 12 consecutive sessions, and doses of 0 (vehicle), 3, 10, and 30 mg/kg JDTic were then administered i.g. to separate groups of 12 rats. Twenty four hours later, the rats were given 15 min of intermittent footshock (0.87 mA, 0.5 s activation time, average inter-activation interval of 40 s) or a 17-mg/kg i.p. administration of cocaine prime followed by a 2-h reinstatement test session. JDTic was also evaluated for its ability to block diuresis induced by the KOR agonist, U50,488H (10 mg/kg, s.c.), during 5-h test sessions beginning 1 h after footshock reinstatement tests to verify its KOR antagonist activity. In the FST, male Sprague-Dawley rats were treated with either nor-binaltorphimine (nor-BNI) or JDTic (both at 0.3, 1, 3, or 10 mg/kg, injected s.c. 23 h before), or desipramine (5.6, 10, or 17 mg/kg, injected i.p. 23, 5, and 1 h before) and placed in a cylinder of water, during which the predominance of immobility, swimming, and climbing were scored during 5-s intervals for 5 min.

RESULTS

The 10- and 30-mg/kg doses of JDTic significantly reduced footshock-induced reinstatement of responding previously reinforced by cocaine and significantly attenuated U50,488H-induced diuresis. In contrast, JDTic did not affect cocaine-prime-induced reinstatement. Both nor-BNI and JDTic decreased immobility and increased swimming time in the FST, similar to the antidepressant desipramine.

CONCLUSIONS

Depression and stress are two states during cocaine abstinence which users identify as precipitating relapse, and JDTic may have properties which attenuate both.