Effects of delaying food availability contingent on ethanol-maintained lever pressing

Behavioral effects of delayed timeouts from reinforcement

Timeouts are sometimes used in applied settings to reduce target responses, and in some circumstances delays are unavoidably imposed between the onset of a timeout and the offset of the response that produces it. The present study examined the effects of signaled and unsignaled timeouts in rats exposed to concurrent fixed-ratio 1 fixed-ratio 1 schedules of food delivery, where each response on one lever, the location of which changed across conditions, produced both food and a delayed 10-s timeout. Delays of 0 to 38 s were examined. Delayed timeouts often, but not always, substantially reduced the number of responses emitted on the lever that produced timeouts relative to the number emitted on the lever that did not produce timeouts. In general, greater sensitivity was observed to delayed timeouts when they were signaled. These results demonstrate that delayed timeouts, like other delayed consequences, can affect behavior, albeit less strongly than immediate consequences.

Drug treatments in criminal justice settings

The available evidence suggests that drug treatment can lead to modest, but real, reductions in criminal offending for drug-using criminal offenders. Considering the scope of the problem of drug-related crime and the expense of dealing with these issues, even marginal improvements can lead to important aggregate savings in both economic and humanitarian terms. More randomized, controlled trials of drug treatment in criminal justice programs will lead to a more sophisticated understanding of what kind of treatment works best for this group.

Effects of punishment on choice between cocaine and food in rhesus monkeys

RATIONALE

Punishment is widely used in an effort to control drug-taking behavior; however, only a few preclinical studies have investigated the effects of punishment on drug self-administration. Such studies may contribute to more rational use of punishment to control drug use.

OBJECTIVES

To evaluate the effects of punishment on choice between cocaine and food in rhesus monkeys.

METHODS

Rhesus monkeys were trained under a concurrent-choice schedule of food delivery (1 g pellets, fixed-ratio 100 schedule) or cocaine injections (0-0.1 mg/kg per injection, fixed-ratio 10 schedule). Full cocaine choice dose-effect curves were determined under baseline conditions and under test conditions in which a putative punisher (intravenous histamine injection; 0.0032-0.032 mg/kg per injection) was paired with either food or cocaine delivery.

RESULTS

Under baseline conditions, cocaine produced a dose-dependent increase in cocaine choice. Histamine functioned as a punisher of both food- and cocaine-maintained responding. Pairing histamine with food delivery reduced food choice, increased cocaine choice, and produced left shifts in the cocaine choice dose-effect curve. Conversely, pairing histamine with cocaine decreased cocaine choice, increased food choice, and produced right shifts in the cocaine choice dose-effect curve. The magnitude of histamine's punishing effects was directly related to histamine dose and probability of histamine delivery, and inversely related to the magnitude of the reinforcer.

CONCLUSIONS

These results demonstrate that a primary effect of punishment in the context of food vs cocaine choice is not only a decrease in the behavior being punished, but also an increase in the unpunished alternative behavior.

Concurrent pentobarbital- and saccharin-maintained responding: effects of saccharin concentration and schedule conditions

Responses of rhesus monkeys were reinforced by delivery of either a pentobarbital (4.0 mg/ml) solution or a vehicle (water) or saccharin solution under a concurrent signaled differential reinforcement of low rates 30-s schedule. After 30 s of no responding, the first response on the pentobarbital or saccharin spout resulted in the delivery of the appropriate solution and reset the timing on both spouts (i.e. a mutually exclusive choice). In the first experiment, the concentration of saccharin was gradually increased across sessions. As saccharin concentration increased, pentobarbital deliveries decreased and saccharin as well as total session deliveries increased. In a second experiment, pentobarbital and 0.24 (mg/ml) saccharin were made available under concurrent signaled differential reinforcement of low rates 30-s schedules which operated independently. Under these conditions responding on one spout had no consequences with respect to the other spout. The reduction of pentobarbital deliveries was substantially attenuated when the choice was not mutually exclusive.

Pharmacological treatment of tobacco dependence

Pharmacologically based approaches for the treatment of tobacco dependence are reviewed. The rational basis for pharmacologic treatment approaches is that tobacco dependence is partially, and critically, mediated by the actions of tobacco-delivered nicotine to the central nervous system. These actions include direct reinforcing properties of nicotine itself, tolerance and physiologic dependence, possible beneficial effects of nicotine in the alleviation of anxiety and control of weight, and neurohormonal regulation which can become important to the maintenance of emotional well-being and performance at work. Insofar as tobacco abstinence leads to negative consequences, via these biobehavioral mechanisms, pharmacologic intervention should be able to assist in initial tobacco detoxification and help tobacco abstinent persons to avoid subsequent relapse. The purpose of this review is to survey some of the efforts to develop such interventions, as well as to elucidate some of the issues relevant to such development. Four distinct approaches are discussed: (1) Nicotine replacement, in which physiologic dependence is transferred to a safer and more therapeutically manageable nicotine delivering formulation; this category includes nicotine polacrilex gum; (2) Blockade therapy, in which a drug is taken that blocks the reinforcing properties of nicotine should relapse occur; (3) Nonspecific pharmacotherapy, in which the biobehaviorally mediated correlates of tobacco abstinence are treated on a symptomatic basis; (4) Deterrent therapy, in which a drug is taken prior to smoking such that any tobacco use would produce reliable aversive effects.

Concurrent phencyclidine and saccharin access: presentation of an alternative reinforcer reduces drug intake

Six monkeys self-administered orally delivered phencyclidine ("angel dust") and saccharin under concurrent fixed-ratio 16 schedules during daily three-hour sessions. Liquid deliveries were contingent upon lip-contact responses on solenoid-operated drinking spouts. Three saccharin concentrations (0.003%, 0.03% and 0.3%, wt/vol) were tested in a nonsystematic order. For each saccharin concentration, the following series of phencyclidine concentrations (mg/ml) was presented: 0.25, 0.5, 1, 0.25 (retest), 0.125, 0.0625, 0.0312, 0.25 (retest) and 0 (water with stimuli signaling phencyclidine). As the saccharin concentration increased, the number of drug deliveries decreased, and the peaks of the concentration-response functions were shifted to the right. The lowest saccharin concentration (0.003%, wt/vol) maintained responding in excess of phencyclidine levels in only one monkey. The two higher saccharin concentrations maintained behavior far in excess of phencyclidine, but saccharin deliveries decreased in some monkeys as phencyclidine concentration and intake (mg/kg) increased. The time course and patterns of phencyclidine-reinforced responding were also altered when saccharin was concurrently available. The results are discussed in terms of strategies to reduce drug-reinforced behavior, preference between different reinforcers, and measures of reinforcing efficacy.

Suppression of ethanol-reinforced lever pressing by delaying food availability

When food was initially available to rats under a fixed-interval 26-second schedule and each liquid-reinforced lever press delayed food availability 8 seconds, suppression of liquid-reinforced lever pressing and liquid consumption occurred when the liquid presented was 4, 8, 16, 32, and 0% ethanol. Suppression did not occur in yoked-control animals, which received food coincidentally with experimental animals but were not directly exposed to the delay dependency. After exposure to the food schedule, each ethanol solution served as a reinforcer in the absence of food presentation. Delaying food availability for increasingly long periods (8 to 2048 seconds) suppressed ethanol-reinforced lever pressing and consumption relative to baseline levels, with the maximum decrease being below the level maintained in the absence of food. However, degree of suppression did not increase monotonically with delay length. Liquid-reinforced performance of yoked-control animals indicated that suppression did not result from changes in the sequencing of food presentation alone.

Attenuation of ethanol intake by contingent punishment of food-maintained responding

Two food-deprived rats responded under a concurrent fixed-ratio 12 (food) fixed-ratio 1 (8% ethanol) reinforcement schedule in which a tone occurred during every second or every fourth interpellet interval. When ethanol-maintained lever presses during the presence of the tone shifted the food schedule to one in which electric shock punishment occurred, ethanol-maintained responding consistently decreased. The decrease in the frequency of ethanol-maintained responding varied directly with shock voltage from 25 to 100 V, and occurred during intervals with the tone present and absent. These results indicate that ethanol intake may be attenuated by contingent changes in a concurrent food schedule.

Effects of d-amphetamine and chlordiazepoxide on positive conditioned suppression

Six rats lever-pressed under a variable-interval 80-sec food reinforcement schedule. After responding had stabilized, an 8-sec tone terminating with food delivery was superimposed on the variable-interval schedule on the average once every five minutes without regard to the animal's behavior. This positive conditioned suppression procedure consistently reduced responding during the pre-food stimulus (tone). Neither d-amphetamine (0.5, 1.0, 2.0 mg/kg) nor chlordiazepoxide (7.5, 15, 30 mg/kg) significantly affected the relative suppression produced by the tone. Instead, both drugs produced generally non-selective effects, similarly affecting response rate in the presence and absence of the tone.