Catecholamine involvement in the narcotic cue
Colpaert, F.C.; Niemegeers, C.J.; Janssen, P.A.
Archives Internationales de Pharmacodynamie et de Therapie 226(2): 339-340
1977
ISSN/ISBN: 0003-9780 PMID: 18121 Document Number: 118754
Narcotic analgesic drugs are known to produce a discriminative stimulus complex of cue, which is highly characteristic of this class of drugs. As narcotics also affect the levels and turnover of brain catecholamines, the possible role of catecholaminergic neurotransmission in the processing of the narcotic cue was investigated. Rats were trained to discriminate 0.04 mg/kg fentanyl (s.c.) from saline. Various groups were pre-treated with .alpha.-methyl-p-tyrosine methyl ester, aceperone, dibenamine, phenoxybenzamine, propranolol, azaperone, chlorpromazine, pipamperone, pimozide or spiperone. The rats were then tested for fentanyl discrimination. All the drugs, except phenoxybenzamine, attenuated total response output. Only pimozide exerted some effect on the narcotic cue and decreased the percentage of responding on the selected lever. The latter effect also was observed with spiperone. A possible noradrenergic involvement in the narcotic cue was not supported; only suggestive evidence for a dopaminergic component was obtained. Specific neuroleptics (haloperidol, pimozide) may affect the euphoric action of narcotics in humans.