Generalization of morphine and lysergic acid diethylamide (LSD) stimulus properties to narcotic analgesics
I. D. Hirschhorn, J. A. Rosecrans
Psychopharmacology January 1, 1976 DOI: 10.1007/bf00428703 via Springer Nature
Summary
In rats trained to distinguish morphine from saline or LSD from saline using a two-lever discrimination task, the stimulus properties of morphine generalized fully to methadone and meperidine, and partially to pentazocine—drugs known to produce morphine-like subjective effects in humans. Morphine's stimulus properties did not generalize to nalorphine or cyclazocine, which produce dissimilar subjective effects. The stimulus properties of LSD generalized partially to cyclazocine but not to nalorphine. In humans, cyclazocine and nalorphine produce a high incidence of psychotomimetic effects, but cyclazocine's subjective effects are differentiable from those of LSD.
Study at a glance
| Characteristics | Animal discrimination study Peer reviewed |
|---|---|
| Population | Rats |
| Keywords | Narcotic analgesic Narcotic antagonist Psychotomimetic Discriminative stimulus |
| Citations | 30 |
| Key finding | The stimulus properties of morphine generalized to methadone and meperidine, and partially to pentazocine, but not to nalorphine or cyclazocine; the stimulus properties of LSD generalized partially to cyclazocine but not to nalorphine. |
Abstract
The present investigation sought to determine whether the stimulus properties of morphine and lysergic acid diethylamide (LSD) would generalize to several narcotic analgesics which vary in their subjective effects. Morphine and saline served as discriminative stimuli for one group of rats in a 2-lever discrimination task. LSD and saline were discriminative stimuli for a second group. Depression of one lever in an operant chamber resulted in reinforcement following the administration of morphine or LSD and the opposite lever was reinforced after saline. After discriminated responding was stable, stimulus generalization tests with narcotic analgesics and antagonists showed that the stimulus properties of morphine generalized to methadone and meperidine, and partially to pentazocine, all of which produce morphine-like subjective effects in humans. Morphine stimulus properties did not generalize to nalorphine or cyclazocine, which produce dissimilar subjective effects. The stimulus properties of LSD generalized partially to cyclazocine, but not to nalorphine. In humans cyclazocine and nalorphine produce a high incidence of psychotomimetic effects, but the subjective effects of cyclazocine are differentiable from those of LSD.