Reinforcing stimulus properties of drugs

Abstract

The reinforcing efficacy of psychoactive drugs can reliably be studied in experimental animals by using procedures for drug self-administration. This property of drugs is used to predict qualitatively and quantitatively their abuse potential in humans. External factors like the dose of the drug, the schedule of drug availability and stimulus control are critically important in initiation, maintenance and cessation of self-administering behaviour. Drug-induced changes in the organism, including tolerance and physical dependence, may contribute more or less to the behaviour associated with drug use and consequently change the pattern of drug intake. Concerning the internal factors involved in the process by which a given drug consequence gains control over behaviour, it is suggested that addictive drugs may mimic the action of endogenous substances which are implicated in the physiological mechanisms underlying reinforcement. Neuropeptides e.g. those related to vasopressin, which are involved in the adaptation of the individual to his environment, may modulate the consequences of drug self-administration by interfering with the complex interaction of addictive drugs with brain homeostatic mechanisms. It is postulated that derangements in neuropeptide systems may be critical factors in the development of addictive behaviour.