In vivo evidence of partial agonist activity exerted by purported 5-hydroxytryptamine antagonists.
Françis C. Colpaert, C J Niemegeers, P A Janssen
European Journal of Pharmacology October 15, 1979 DOI: 10.1016/0014-2999(79)90326-1 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Animal behavioral pharmacology experiment (drug discrimination) Peer reviewed |
|---|---|
| Sample size | 9 |
| Population | Rats trained in a food-reinforced two-lever operant drug-discrimination task |
| Interventions | LSD cyproheptadine methysergide mianserin mescaline quipazine |
| Dose | LSD 0.16 mg/kg; cyproheptadine 1.25 and 10 mg/kg; methysergide 0.16 to 10 mg/kg; mianserin 2.5 to 40 mg/kg; mescaline 5 to 40 mg/kg; quipazine 1.25 to 5 mg/kg |
| Key findings | Rats trained to discriminate 0.16 mg/kg LSD from saline showed partial generalization to the purported 5-HT antagonists cyproheptadine, methysergide and mianserin, and full generalization to the hallucinogens mescaline and quipazine. The authors suggest the three antagonists may exert partial agonist effects at central 5-HT receptors in addition to their antagonist action. |
Abstract
Using a food-reinforced two-lever operant method, rats (n = 9) were trained to discriminate 0.16 mg/kg LSD from saline. Tests for stimulus generalization in rats so trained indicated that the purported 5-HT antagonists cyproheptadine (1.25 and 10 mg/kg), methysergide (0.16 to 10 mg/kg) and mianserin (2.5 to 40 mg/kg) produced partial generalization with LSD. The hallucinogens mescaline (5 to 40 mg/kg) and quipazine (1.25 to 5 mg/kg) were also generalized with LSD. The data suggest that cyproheptadine, methysergide and mianserin may produce partial agonist effects in addition to their antagonist action at central 5-HT receptor sites.
Citations in the library
Cited by 5
- Role of 5-HT2A and 5-HT2C receptors in the stimulus effects of hallucinogenic drugs. II: Reassessment of LSD false positives. Psychopharmacology October 1995
- Complex stimulus properties of LSD: a drug discrimination study with alpha 2-adrenoceptor agonists and antagonists. Psychopharmacology August 1995
- The time-dependent stimulus effects of R(-)-2,5-dimethoxy-4-methamphetamine (DOM): implications for drug-induced stimulus control as a method for the study of hallucinogenic agents. Psychopharmacology May 1995
- Interactions between serotonergic agonists and antagonists in rats trained with LSD as a discriminative stimulus. Pharmacology, Biochemistry, and Behavior July 1988
- Behavioral and 5-HT antagonist effects of ritanserin: a pure and selective antagonist of LSD discrimination in rat. Psychopharmacology 1985