Nitrous oxide is a gas at room temperature and pressure. It is used primarily for anesthesia but is also used as a propellant for whipped cream or to boost octane levels in racing cars. N2O was extensively studied by Sir Humphrey Davy, who presented a detailed description of his subjective experiences under the influence of N2O, as well as self-reports by friends and colleagues of their own experiences while inhaling the gas. Sir Davy's treatise was a thorough, systematic, and extensive (...) characterization of N2O and was a foreshadowing of two centuries of research to follow. Sir Davy's and subsequent research consisted of the dose-response assessment of subjective effects of acute and repeated N2O administration, examination of individual differences, and the study of environmental and organismic determinants/modulators of N2O effects. This chapter presents the results of such experiments in a chronological framework and attempts to detail the various characterizations of N2O across the years since its discovery. (shrink)

Opioids, which have long been abused, are capable of producing euphoria and other “positive” subjective effects. Although the relationship between positive subjective effects and abuse of a drug is not necessarily causal, there is a predictive relationship between those drugs that produce a positive spectrum of subjective effects and their likelihood of functioning as reinforcers and being abused. A host of factors influence the subjective effects of opioids ; some of the more salient ones are covered in this chapter. It (...) first describes how subjective effects of opioids are measured and then discusses how such factors as dose, route of administration, rate of onset of drug effects, tolerance and dependence, and drug use history can all influence an opioid's subjective effects. (shrink)