Springer Online Journal Archives 1860-2000
Abstract The discriminative stimulus (DS) effects of smoked marijuana were studied by training marijuana smokers to discriminate between the effects of marijuana containing 2.7% △9-THC (M) and marijuana containing 0.0% △9-THC (P). In addition to measures of discrimination responding, subjective effects were assessed with standardized mood questionnaires. The post-smoking increase in expired air carbon monoxide (CO) level was used as an index of smoke inhalation. Relative to P cigarettes, M cigarettes increased heart rate and produced changes on eight mood scales. M cigarettes were rated as harsher and more potent than P cigarettes, and produced lower levels of CO than P cigarettes. The P-M discrimination was readily acquired by most subjects. The DS effects of marijuana showed a rapid onset, appearing within 90 s from the beginning of smoking. The DS effects were dose dependent, with 0.9% △9-THC marijuana producing primarily placebo-appropriate discrimination responding, and 1.4% △9-THC marijuana producing 100% drug-appropriate responding. This experimental paradigm could be used to determine whether the DS effects of smoked marijuana would generalize to those of other psychoactive drugs.
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