CLASSICAL-CONDITIONING IN HUMANS - NICOTINE AS CS AND ALCOHOL AS US

Animal studies suggest that drug effects can act as conditioned stimul i for various unconditioned stimuli including the effects of other dru gs. The current study investigated drug-drug conditioning in human sub jects. Sixteen subjects were given subcutaneous injections of either n icotine or saline before consumption of an alcoholic or soft drink in each of eight sessions. Across sessions the content of the injections was established as a reliable predictor of the alcoholic content of th e drink. Physiological, subjective, and behavioural responses to the i njections were used as indices of conditioning. Skin conductance measu res obtained following the injections changed across trials in a way c onsistent with a conditioned response though patterns of change on car diac inter-beat interval were less clear. However, neither behavioural nor subjective measures showed conditioning effects. In view of the n umber of variables studied the evidence for the development of conditi oned responding on physiological measures must be suspected of being a type I error and is in need of replication. Subjects' reports reveale d that nicotine and saline injections were difficult to discriminate. This would have weakened conditioning effects. Suggestions are made fo r improvements in the design of future studies of drug-drug conditioni ng in human subjects.