THE REINFORCING EFFECTS OF BRIEF EXPOSURES TO NITROUS-OXIDE IN HEALTHY-VOLUNTEERS

The reinforcing and subjective effects of brief(about 1.5 min) exposur es to nitrous oxide, ranging from inspired concentrations of 20-80% in oxygen, were examined in 11 healthy volunteers. A choice procedure wa s used in which during each of four sessions, subjects first sampled a given concentration of nitrous oxide and placebo oxygen, and then cho se between the two. 20, 40, 60 and 80% nitrous oxide were chosen by fi ve, four, three, and three subjects, respectively-these choice levels did not exceed that of chance. All concentrations had psychoactive eff ects, and in general, concentration-related subjective effects were fo und. We conclude that in a medical setting, nitrous oxide inhaled in a manner similar to that when used recreationally in a naturalistic set ting, does not function as a reinforcer across a wide range of concent rations, in subjects with a modest lifetime history of psychoactive dr ug use.