Biomedical subjects

N M Petry

Publications and source records attributed to N M Petry.

45 records · Page 3Linked to original sources

PubMed1998

Shortened time horizons and insensitivity to future consequences in heroin addicts.

AIMS: To investigate whether heroin addicts demonstrate shortened time horizons and decreased sensitivity to future consequences of their behavior compared to non-drug users. DESIGN SETTING AND PARTICIPANTS: Thirty-four heroin addicts enrolled in a buprenorphine treatment clinic and 59 non-drug-using controls completed a personality questionnaire and two laboratory tasks. MEASUREMENTS: The Stanford Time Perception Inventory (STPI) personality questionnaire assessed orientation to the future, and the Future Time Perspective (FTP) task elicited predictions of the timing and ordering of future events. The Bechara card task measured preferences for decks of cards that range in magnitude and probability of delayed and immediate rewards and punishers. FINDINGS: Heroin addicts scored significantly lower than controls on the STPI scale indicative of future orientation. In the FTP, heroin addicts were less likely to predict events far into the future and less likely to systematically organize events in the future. In the card task, heroin addicts were less likely to win money than controls. They were more likely to play from a deck that contained greater immediate gains but that resulted in large, delayed punishers and overall net losses. They also made fewer selections from a deck that provided an overall net gain via relatively low immediate rewards and frequent small punishments. CONCLUSIONS: Shortened time horizons and decreased sensitivity to delayed consequences may explain drug abusers' persistent use of drugs, despite the long-term negative consequences associated with drug use.

Adolescent↗

PubMed1998

A behavioral intervention for improving verbal behaviors of heroin addicts in a treatment clinic.

Positively reinforcing appropriate behaviors improved verbal behaviors of opioid-dependent patients in a buprenorphine treatment clinic. During B phases of an ABAB design, clients received stickers for engaging in appropriate verbal or nonverbal behaviors. Each sticker provided a chance of winning $25. No reinforcement was provided during the A phases. Appropriate verbal behaviors increased during reinforcement periods, and inappropriate verbal behaviors decreased.

Adult↗

PubMed1998

A 12-year study (1975-1986) of mortality in methadone-maintenance patients: selected demographic characteristics and drug-use patterns of AIDS and non-AIDS-related deaths.

This paper describes changes in demographic characteristics and drug use patterns of persons who died while enrolled in a New York City methadone-maintenance program during the years preceding and subsequent to the AIDS epidemic. Persons dying from AIDS were more likely to be younger, Hispanic, and male than those dying from other causes. Drug use increased during the 12-year study period, and the spread of the HIV infection among drug users may be reflected in an increased use of injectable drugs.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Bidirectional modulation of sweet and bitter taste by chlordiazepoxide and Ro 15-4513: lack of effect with GABA drugs.

Five rats were trained to respond for 10% sucrose and 10% sucrose/0.006% quinine in an operant procedure. Both solutions were concurrently available on independent, variable-interval 5-s schedules of reinforcement. Rats reliably responded for both solutions throughout the sessions and made approximately 68% of their total daily responses for the sucrose solution. When injected prior to the sessions with 4 mg/kg of chlordiazepoxide, rats selectively increased quinine responding; injections of the benzodiazepine inverse agonist Ro 15-4513 (9 mg/kg) led to decreased quinine responding. The effects of both chlordiazepoxide and Ro 15-4513 were reversed by the benzodiazepine antagonist flumazenil. Presession injections of flumazenil, muscimol, baclofen, or picrotoxin all resulted in no changes in responding, or a decrease in responding for both solutions. These results are discussed in terms of a bidirectional modulation of sweet-bitter taste preference by drugs acting on the benzodiazepine receptor. Moreover, the data from these experiments suggest that any changes in the oral consumption of alcohol following administration of benzodiazepine drugs must be examined in light of their effects on taste palatability.

Animals↗

PubMed1997

Impulsive and self-control choices in opioid-dependent patients and non-drug-using control participants: drug and monetary rewards.

Delay discounting was investigated in opioid-dependent and non-drug-using control participants. The latter participants were matched to the former on age, gender, education, and IQ. Participants in both groups chose between hypothetical monetary rewards available either immediately or after a delay. Delayed rewards were $1,000, and the immediate-reward amount was adjusted until choices reflected indifference. This procedure was repeated at each of 7 delays (1 week to 25 years). Opioid-dependent participants were given a second series of choices between immediate and delayed heroin, using the same procedures (i.e., the amount of delayed heroin was that which could be purchased with $1,000). Opioid-dependent participants discounted delayed monetary rewards significantly more than did non-drug-using participants. Furthermore opioid-dependent participants discounted delayed heroin significantly more than delayed money.

Adolescent↗

PubMed1997

Benzodiazepine-GABA modulation of concurrent ethanol and sucrose reinforcement in the rat.

These experiments examined the role of the benzodiazepine (BZ)-GABA receptor complex in modulating ethanol consumption in rats. Lever presses were reinforced with concurrently available, isocaloric solutions: 10% ethanol-10% sucrose and 24% sucrose. Both reinforcers were available on independent, variable-interval 5-s schedules of reinforcement. In baseline sessions, rats earned approximately 110 sucrose reinforcers and 131 ethanol-sucrose reinforcers, equivalent to about 2 g ethanol per kilogram of body weight. Before experimental sessions, rats received injections of Ro 15-4513, Ro 15-1788, and Ro 15-4513 in combination with Ro 15-4513, chlordiazepoxide, picrotoxin, baclofen, and muscimol. Responding for the ethanol solution was significantly and selectively reduced by the BZ inverse agonist Ro 15-4513, and this effect was blocked by administration of the BZ antagonist Ro 15-1788. Conversely, responding for the ethanol solution increased following a low dose of the BZ agonist chlordiazepoxide. A low dose of baclofen significantly decreased responding for sucrose and increased consumption of ethanol. Picrotoxin and muscimol selectively reduced responding for the ethanol solution. These results are discussed in terms of the relationship between the BZ-GABA receptor complex and ethanol consumption.

Alcohol Drinking↗

PubMed1995

Ro 15-4513 selectively attenuates ethanol, but not sucrose, reinforced responding in a concurrent access procedure; comparison to other drugs.

The experiments described in this report used a concurrent access procedure to study ethanol reinforcement. Rats were trained to lever press for a 10% sucrose solution and a 10% ethanol/10% sucrose mixture, and both reinforcers were available on variable-interval 5-s schedules. In baseline and vehicle injection sessions, the animals distributed their responding between both solutions. When injected with the partial inverse benzodiazepine agonist Ro 15-4513 (3, 9, and 18 mg/kg), responding for the ethanol solution decreased while responding for sucrose remained intact. Ethanol injections (0.5 and 1.0 g/kg) engendered a similar profile. Chlordiazepoxide led to an increase in ethanol mix responding at 2 mg/kg and a decrease in ethanol mix responding at higher doses; no dose affected sucrose responding. Morphine (0.5-16 mg/kg) decreased responding for both the ethanol mix and sucrose solutions, more or less simultaneously. Naloxone (0.125-20 mg/kg) selectively reduced ethanol mix responding at low doses, and decreased responding for both reinforcers at high doses. In another group of animals, isocaloric alternatives were concurrently available: 10% ethanol/0.25% saccharin versus 14% sucrose. Injections of Ro 15-4513 and chloridiazepoxide produced similar results as in the first group of rats: an increase in ethanol mix responding with low dose chlordizepoxide, and a decrease in ethanol mix responding with Ro 15-4513. However, naloxone injections did not selectively affect responding for either of the reinforcers when they were isocaloric. These results are discussed in terms of ethanol's neuropharmacological actions.

Animals↗

PubMed1995

Behavioral economics of concurrent ethanol-sucrose and sucrose reinforcement in the rat: effects of altering variable-ratio requirements.

These experiments examined the own-price and cross-price elasticities of a drug (ethanol mixed with 10% sucrose) and a nondrug (10% sucrose) reinforcer. Rats were presented with ethanol-sucrose and sucrose, both available on concurrent independent variable-ratio (VR) 8 schedules of reinforcement. In Experiment 1, the variable ratio for the ethanol mix was systematically raised to 10, 12, 14, 16, 20, and 30, while the variable ratio for sucrose remained at 8. Five of the 6 rats increased ethanol-reinforced responding at some of the increments and defended baseline levels of ethanol intake. However, the rats eventually ceased ethanol-reinforced responding at the highest variable ratios. Sucrose-reinforced responding was not systematically affected by the changes in variable ratio for ethanol mix. In Experiment 2, the variable ratio for sucrose was systematically increased while the ethanol-sucrose response requirement remained constant. The rats decreased sucrose-reinforced responding and increased ethanol-sucrose-reinforced responding, resulting in a two- to 10-fold increase in ethanol intake. Experiment 3 examined the substitutability of qualitatively identical reinforcers: 10% sucrose versus 10% sucrose. Increases in variable-ratio requirements at the preferred lever resulted in a switch in lever preference. Experiment 4 examined whether 10% ethanol mix substituted for 5% ethanol mix, with increasing variable-ratio requirements of the 5% ethanol. All rats eventually responded predominantly for the 10% ethanol mix, but total amount of ethanol consumed per session did not systematically change. In Experiment 5, the variable-ratio requirements for both ethanol and sucrose were simultaneously raised to VR 120; 7 of 8 rats increased ethanol-reinforced responding while decreasing sucrose-reinforced responding. These data suggest that, within this ethanol-induction procedure and within certain parameters, demand for ethanol-sucrose was relatively inelastic, and sucrose consumption was independent of ethanol-sucrose consumption. Demand for sucrose, on the other hand, was relatively elastic, and ethanol-sucrose readily substituted for it. The results are discussed in terms of applying a behavioral economic approach to relationships between drug and nondrug reinforcers.

Alcohol Drinking↗

PubMed1994

Effects of qualitatively different reinforcers on the parameters of the response-strength equation.

This experiment examined the relationship between two qualitatively different reinforcers and the parameters of a quantitative model of reinforced responding, referred to as the response-strength equation or the Herrnstein equation. A group of rats was first food deprived and later water deprived. An 11.5% sucrose solution served as the reinforcer in the food-deprivation condition, and water was the reinforcer in the water-deprivation condition. Each experimental session consisted of a series of seven variable-interval schedules, providing reinforcement rates that varied between 20 and 1,200 reinforcers per hour. The response rates increased in a negatively accelerating function in a manner consistent with the response-strength equation. This equation has two fitted parameters, k and Re. According to one theory, the k parameter is a measure of motor performance, and Re is indicative of the relative reinforcement efficacy of the background uncontrollable sources of reinforcement in relation to the experimentally arranged reinforcer. In this study, k did not change as a result of the different reinforcers, but Re was significantly larger in the sucrose-reinforcement condition. These results are consistent with the interpretation that k and Re measure two independent and experimentally distinguishable parameters and provide further evidence that absolute response rate is a function of relative reinforcement rate, as implied by the derivation of the response-strength equation based on the matching law.

Animals↗