Schedule-induced self injection of drugs.

The schedule-induced polydipsia paradigm has been used to induce oral ingestion of large volumes of alcohol, barbiturate and other drug solutions. We have developed a method of schedule-induced self injection which allows the study of acquisition and maintenance of drug intake behaviour in changing environments free from the interference of taste factors or imbalances due to excessive water intake. In this paper we review our findings on the acquisition and maintenance patterns of amphetamine, methadone, heroin, alcohol, nicotine, cocaine, delta 9-THC and haloperidol . For all drugs except amphetamine, the combination of schedule and nutritional deprivation leads to the highest rates of drug intake although the schedule does not appear to be a potent factor at free feeding weight. Drug intake is the result of the interaction of environmental factors and pharmacological properties of the drugs, rather than the effects of drug or environmental factors separately . From a number of preliminary studies, data on corticosterone response in drug self-injection behaviour and the function of the nucleus accumbens septum are presented.