Progressive ratio schedule of reinforcement

Ranaldi, R., Wise, R.A. Intravenous self-administration of methamphetamine-heroin (speedball) combinations under a progressive-ratio schedule of reinforcement in rats. Neuroreport. 11 2621, 2000. 

Roberts DCS, Bennett SAL (1993) Heroin self-administration in rats under a progressive ratio schedule of reinforcement. Psychopharmacology 111 215-218 Shelton KL (2007) Inhaled toluene vapor as a discriminative stimulus. Behav Pharmacol 18 219-229... 

Solinas M, Panlilio LV, Antoniou K, Pappas LA, Goldberg SR. The cannabinoid CB 1 antagonist N-piperidinyl-5-(4-chlorophenyl)-l-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide (SR-141716A) differentially alters the reinforcing effects of heroin under continuous reinforcement, fixed ratio, and progressive ratio schedules of drug self-administration in rats. J. Pharmacol. Exp. Ther. 306, 93-102 (2003). 

Another indicator of the reinforcing effectiveness of a test substance can be the amount of work an animal will perform to obtain the test substance. This can be investigated with a progressive ratio schedule whereby the response requirement increases for every infusion (Solinas et al. 2004) or after a fixed period of time (Wilcox et al. 2000) until the animal ceases to lever-press for a pre-determined interval,... 

Evidence for a role of NAc DA in cocaine reinforcement has been provided by studies of the effect of 6-OHDA lesions on cocaine self-administration. Thus, 6-OHDA lesions of the DA innervation of the nucleus accumbens result in extinction-like effects on responding for cocaine in FR schedules (Roberts et al., 1977 Roberts et al., 1980, Pettit et al., 1984) and in a decrease in break point in progressive ratio schedules (Koob et al.,... 

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