Cocaine self-injection behaviour under schedules of delayed reinforcement in monkeys

Abstract

Rates of lever pressing, maintained either by response-dependent intravenous injections of cocaine (250 mug/kg per injection) or by food-pellet presentation, were compared and found to vary systematically as a function of the delay (5-100 s) imposed between the response(s) and the occurrence of reinforcement. The control of responding by two schedules of delayed reinforcement was studied. The first scedule permitted responses to occur during the delay period without any programmed consequence; the second schedule required a response, and then the elapse of x seconds without any additional response(s). At imposed delays of 50 and 100 s, response rates were reduced significantly when the second schedule was in effect by comparison with the first. The effect was observed when responding was maintained either by intravenous cocaine injections or by food-pellet presentation. Across all comparable conditions, response rates were higher when maintained by scheduled cocaine injections than by food pellets. Rate enhancement, generally induced by drugs of the psychomotor stimulant type, could account for the observed difference.

Effects of delay to reinforcement on the choice between cocaine and food in rhesus monkeys

“…The effects of delay were qualitatively similar when the alternative to an injection of 0.05 mg/kg cocaine was a lower dose of cocaine. This result is consistent with previous reports that a delay to reinforcement can decrease choice of the delayed injection of equal doses of cocaine (Anderson and Woolverton 2003; see also Beardsley and Balster 1993;Stretch et al 1976). Thus, delay to reinforcement can reduce the reinforcing effectiveness of an injection of cocaine, whether the alternative is a non-drug or drug reinforcer.…”

“…Drug self-administration research involving animal subjects has established that, as with choice between non-drug reinforcers, relative reinforcer magnitude (Carroll 1985;Nader and Woolverton 1991), cost (Carroll et al 1991;Meisch and Lemaire 1988;Nader and Woolverton 1992), frequency (Anderson et al 2002;Anderson and Woolverton 2000) and probability (Woolverton and Rowlett 1998) can alter drug choice. Although delay has been shown to decrease self-administration under simple schedules of reinforcement (Beardsley and Balster 1993;Stretch et al 1976), the effects of delay on drug choice has received little experimental attention (for a review, see Anderson and Woolverton 2003). In humans, the rate of temporal discounting of reinforcers has been reported to be greater in substance abusers relative to control subjects (Madden et al 1997;Vuchinich and Simpson 1998;Kirby et al 1999;Petry and Casarella 1999) and, thus, may be an important determinant of the choice between drug and non-drug reinforcers.…”

A Comparison of Responding Maintained Under Second‐order Schedules of Intramuscular Cocaine Injection or Food Presentation in Squirrel Monkeys

“…A view that the effects of changes in stimulus duration are due primarily to delay in presentation of the maintaining event could explain those findings and the descending portions of the functions in Figure 8 (cf. Dews, 1960;Ferster, 1953;Skinner, 1938;Stretch, Gerber, & Lane, 1976). In the present study, however, rates of both cocaine-and food-maintained responding were highest at intermediate stimulus durations, suggesting other factors influencing performance.…”

Place Conditioning and Locomotor Effects of N-Substituted, 4′,4′′-Difluorobenztropine Analogs in Rats

“…As previously mentioned, delays in onset of effect can substantially diminish the effectiveness of a drug reinforcer (e.g., Balster and Schuster, 1973;Stretch et al, 1976;Beardsley and Balster, 1993;Panlilio et al, 1998). However, with delays between treatment and placement in the chamber place-conditioning procedures can be sensitive to effects of drugs with delayed onsets of action (De Beun et al, 1992).…”

“…Regardless of the source, a delay in the onset of action of BZT analogs could account for the differences between cocaine and BZT analogs in studies of their reinforcing effects. Because self-administration procedures involve the direct reinforcement of a response with the injection of drug, a small delay in onset of effect could act like a delay in reinforcement, and decrease the rate of responding maintained by the drug (e.g., Gollub and Yanagita, 1974;Stretch et al, 1976;Beardsley and Balster, 1993; see also Lile et al, 2003).…”