Progressive-ratio schedules of drug delivery in the analysis of drug self-administration: a review

145

177

Accumulating evidence indicates that dopamine (DA) D 3 receptor antagonists appear highly promising in attenuating cocaine reward and relapse in preclinical models of addiction. In the present study, we investigated the effects of the novel D 3 -selective antagonist NGB 2904 (N-(4-[4-{2,3-dichlorophenyl}-1-piperazinyl]butyl)-3-fluorenylcarboxamide) on cocaine self-administration, cocaine-enhanced brain stimulation reward (BSR), and cocaine-triggered reinstatement of drug-seeking behavior in male Long-Evans rats. We found that: (1) acute intraperitoneal (i.p.) administration of NGB 2904 (0.1-10 mg/kg) failed to alter cocaine self-administration (0.5 mg/kg/infusion) under fixed-ratio 2 (FR2) reinforcement, but 1 or 5 mg/kg NGB 2904 significantly lowered the break-point for cocaine self-administration under progressive-ratio (PR) reinforcement; (2) cocaine (1, 2, and 10 mg/kg) significantly enhanced electrical BSR (decreased brain reward thresholds), while NGB 2904 significantly inhibited the enhancement of BSR elicited by 2 mg/kg, but not 10 mg/kg of cocaine; (3) NGB 2904 alone neither maintained self-administration behavior nor altered brain reward thresholds; and (4) NGB 2904 significantly inhibited cocaine-triggered reinstatement of extinguished drug-seeking behavior, but not sucrose-plus-sucrose-cue-triggered reinstatement of sucrose-seeking behavior. Overall, these data show that the novel D 3 -selective antagonist NGB 2904 attenuates cocaine's rewarding effects as assessed by PR self-administration, BSR, and cocaine-triggered reinstatement of cocaine-seeking behavior. Owing to these properties and to its lack of rewarding effects (as assessed by BSR and by substitution during drug self-administration), NGB 2904 merits further investigation as a potential agent for treatment of cocaine addiction.

Section: Ngb 2904's Inhibition Of Cocaine Self-administration Under Pmentioning

confidence: 72%

Section: Ngb 2904's Inhibition Of Cocaine Self-administration Under Pmentioning

confidence: 99%

The Novel Dopamine D3 Receptor Antagonist NGB 2904 Inhibits Cocaine's Rewarding Effects and Cocaine-Induced Reinstatement of Drug-Seeking Behavior in Rats

Newman

Gilbert

et al. 2005

145

177

“…Together, these results suggest that these cocaine analogs would have psychostimulant-like abuse potential. By progressively increasing response requirement, a PR schedule measures the maximum amount of behavior that a subject emits for a reinforcer, thereby allowing a quantitative estimate of the reinforcing strength or efficacy (see Depoortere et al, 1993;Stafford et al, 1998). When measured under the present PR schedule, the order of the maximum number of injections was cocaine4WIN 354284RTI 31XRTI 51.…”

Section: Discussionmentioning

confidence: 99%

A Reduced Rate of In Vivo Dopamine Transporter Binding is Associated with Lower Relative Reinforcing Efficacy of Stimulants

Wee

2005

A slow onset of action has been hypothesized to weaken the reinforcing effects of drugs. The present study evaluated this hypothesis with slow-onset cocaine analogs, WIN 35428, RTI 31, and RTI 51. When cocaine or a cocaine analog was made available to rhesus monkeys (n ¼ 4 or 5) for self-administration under a progressive-ratio (PR) schedule with a 1-h time-out between injections, all the drugs functioned as positive reinforcers. The maximum number of injections was in the order of cocaine4WIN 354284RTI 314RTI 51. In in vivo binding in rat striatum, equipotent doses of cocaine, WIN 35428, RTI 31, and RTI 51 were estimated to displace 25% of [ 3 H]WIN 35428 binding at the dopamine transporters (DAT), respectively, 5.8, 22.4, 30.8, and 44.1 min after the intravenous injection. Further, relative reinforcing efficacy was correlated with rate of DAT binding such that slower displacement of [ 3 H]WIN 35428 was associated with a weaker reinforcing effect. In in vitro binding in monkey brain tissue, the cocaine analogs had higher affinity for monoamine transporter sites, but similar affinity ratios of 5-HTT/DAT, compared to cocaine. Lastly, RTI 31 was shown to function as a positive reinforcer in drug-naïve rhesus monkeys under a fixed-ratio 1 schedule. Collectively, the data support the hypothesis that a slow onset at the DAT is associated with reduced reinforcing efficacy of DAT ligands. The data under both the PR and FR schedules, however, suggest that a slow onset at the DAT influence reinforcing effect only to a limited extent.

“…The PR schedule is regarded as a valid procedure for assessing the reinforcing efficacy of drugs of abuse (Richardson and Roberts, 1996;Stafford et al, 1998), and it has been used to assess nicotine's reinforcing efficacy in laboratory animals and humans (Risner and Goldberg, 1983;Donny et al, 1999;Harvey et al, 2004). Since early onset of tobacco use is associated with a higher probability of relapse during abstinence (Cui et al, 2006), a further objective was to assess the reinstatement of nicotine seeking induced by acute reexposure to the drug (nicotine priming) in nicotine-free adult rats that were trained to self-administer nicotine either during adolescence or adulthood using the reinstatement model, an animal model of relapse to drug seeking Epstein et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Nicotine Self-Administration, Extinction Responding and Reinstatement in Adolescent and Adult Male Rats: Evidence Against a Biological Vulnerability to Nicotine Addiction during Adolescence

Shram

Funk

et al. 2007

Initiation of smoking behavior typically occurs during adolescence and rarely occurs during adulthood. Despite this epidemiological evidence, relatively little is known about possible neurobiological differences in the response to nicotine in adolescents that might make them more vulnerable to nicotine addiction. In the current study, we assessed nicotine self-administration under fixed ratio (FR) and progressive ratio (PR) reinforcement schedules in adolescent (postnatal day (P) 33-35) and adult (P91-94) rats. We then assessed extinction and reinstatement of nicotine seeking in adulthood in rats that initiated nicotine self-administration during either adolescence or adulthood. Nicotine self-administration (0.03 mg/kg/infusion, i.v.) was higher in adult rats than in adolescent rats under FR5 and PR reinforcement schedules; no age differences in nicotine self-administration were observed under FR1 or FR2 reinforcement schedules. In contrast, saccharin self-administration under FR5 and PR reinforcement schedules was similar in both age groups, potentially ruling out age differences in general performance. Rats that initiated nicotine self-administration as adults demonstrated a greater resistance to extinction of nicotine taking behavior when saline was substituted for nicotine than rats that initiated self-administration as adolescents. Reinstatement of nicotine seeking following nicotine priming injections (0.075, 0.15, 0.3 mg/kg, s.c.) was independent of the age of onset of nicotine self-administration. The present data from established rat models of drug self-administration and drug relapse suggest that nicotine is less reinforcing in adolescent compared with adult rats and that processes other than the reinforcing effects of nicotine may be involved in the greater susceptibility to smoking during the adolescent developmental stage.