Lack of evidence for context-dependent cocaine-induced sensitization in humans: preliminary studies

Addiction: Taking the brain seriously

Heyman's target article is an analytical tour de force, but it makes too hard a distinction between voluntary and driven behavior. It is more fruitful to think about brain and behavior as shifting, interacting “agents,” represented by multiple neural circuits. This has the virtue of better connecting behavioral analysis with wet neuroscience.

Heyman's steady-state theory of addiction

Heyman's target article contributes to our understanding of addictions by offering solutions to several paradoxes and by recognizing the stable nature of addictive behavior. Previous classical and operant conditioning models have emphasized molecular processes, such as acquisition and extinction, and have failed to address the aggregate effects of long-term exposure to the contingencies of drug and alcohol use.

Matching observation to addiction theory

Over the years, many theories have been proposed to account for the aberrant behavior of drug dependent individuals. Heyman posits that the existing theories of drug dependence are inadequate to explain the complex processes inherent in human drug-taking. He proposes that incongruous behaviors that comprise addiction, such as continued drug use in spite of adverse consequences, can be explained by application of the matching law approach. While the matching law theory of addiction explains certain aspects of human behavior, its application to the area of addiction must be subjected to experimental verification.

The biological, social and clinical bases of drug addiction: commentary and debate

This article summarizes the main discussions at a meeting on the biological, social and clinical bases of drug addiction focused on contemporary topics in drug dependence. Four main domains are surveyed, reflecting the structure of the meeting: psychological and pharmacological factors; neurobiological substrates; risk factors (including a consideration of vulnerability from an environmental and genetic perspective); and clinical treatment. Among the topics discussed were tolerance, sensitization, withdrawal, craving and relapse; mechanisms of reinforcing actions of drugs at the behavioural, cognitive and neural levels; the role of subjective factors in drug dependence; approaches to the behavioural and molecular genetics of drug dependence; the use of functional neuroimaging; pharmaceutical and psychosocial strategies for treatment; epidemiological and sociological aspects of drug dependence. The survey takes into account the considerable disagreements and controversies arising from the discussions, but also reaches a degree of consensus in certain areas.

Effects of intravenous cocaine on plasma cortisol and prolactin in human cocaine abusers

The aim of the present work was to examine the cortisol and prolactin responses to acute cocaine administration in human cocaine users. Each subject served as his own control during intravenous saline placebo and cocaine (40 mg) infusion sessions. Cocaine significantly elevated plasma cortisol but did not affect prolactin. The rise in cortisol coincided with an increase in heart rate and blood pressure after cocaine. In agreement with studies in animals, our data suggest that cocaine activates the hypothalamic-pituitary-adrenal axis in humans. However, based on the well-known importance of dopamine as a prolactin-inhibiting factor, the failure of cocaine to suppress prolactin in the present study raises questions concerning the role of dopamine in the mechanism of acute cocaine action in humans.

A review of the effects of dopaminergic agents on humans, animals, and drug-seeking behavior, and its implications for medication development. Focus on GBR 12909

Medication development for cocaine abuse has focused on potential mechanisms of action related to the abuse of cocaine. The hypothesis that mesolimbic dopamine (DA) is the key neurochemical mediator of cocaine's addictive and reinforcing effects is well supported by a wide variety of data from animal studies. On the other hand, medications that increase DA or block its action in humans can produce effects that appear incompatible with this hypothesis. This article reviews these incompatibilities between animal and human data with a focus on the DAergic actions of drugs, including DA reuptake inhibitors, direct DA agonists, DA increasers, and DA antagonists. Possible reasons for these discrepancies are discussed, and the potential role of high-affinity DA uptake inhibitors, such as GBR12909, for pharmacotherapies for treating cocaine addiction in humans is likely to come from understanding its mechanisms of action, it is clear that further research on the effects of cocaine in humans and animals will be critical to the medication development effort.