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Evidence against an involvement of the haloperidol‐sensitive σ recognition site in the discriminative stimulus properties of (+)‐N‐allylnormetazocine ((+)‐SKF 10,047)
Author(s) -
Singh L.,
Wong E.H.F.,
Kesingland A.C.,
Tricklebank M.D.
Publication year - 1990
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1990.tb14668.x
Subject(s) - haloperidol , nmda receptor , pharmacology , chemistry , stimulus control , binding site , antagonist , pentazocine , dextrorphan , receptor , stereochemistry , neuroscience , psychology , biochemistry , analgesic , medicine , dopamine , nicotine
1 The involvement of the haloperidol‐sensitive, σ recognition site and the N‐methyl‐ d ‐aspartic acid (NMDA) receptor in the mediation of the discriminative stimulus properties of (+)‐N‐allylnormetazocine ((+)‐NANM, (+)‐SKF 10,047), has been investigated in the rat by use of a two‐lever, operant drug discrimination paradigm. 2 Six compounds with nanamolar affinity for the σ recognition site ((±)‐pentazocine, (+)‐3‐(hydroxyphenyl)‐N‐propylpiperidine ((+)‐3‐PPP), ditolylguanidine (DTG), haloperidol, (−)‐butaclamol and BMY 14802) were investigated for their ability to generalise or antagonise the (+)‐NANM discriminative stimulus. Each drug was tested at doses found in an ex vivo radioligand binding assay to displace [ 3 H]‐DTG from the central σ recognition site by more than 40%. 3 While (±)‐pentazocine (in the presence of naloxone) generalised and (+)‐3‐PPP partially antagonised the (+)‐NANM cue, the other putative σ ligands were ineffective either as agonists or antagonists at doses clearly occupying the σ site in vivo . 4 Dose‐dependent generalisation to the (+)‐NANM cue was seen with the selective non‐competitive NMDA receptor antagonist, MK‐801, a compound devoid of significant affinity for the σ recognition site. 5 (±)‐Pentazocine was found to antagonise seizures induced in the mouse by NMDLA, a model reflecting antagonism of central NMDA receptors, and a strong correlation was found between the rank order of potency of compounds to generalise to the (+)‐NANM discriminative stimulus and their potencies as anticonvulsants. 6 In conclusion, no evidence was found to substantiate the contention that the discriminative stimulus properties of (+)‐NANM are mediated by the haloperidol‐sensitive σ recognition site. On the other hand, the results are consistent with the interoceptive stimulus being mechanistically based in the NMDA receptor complex.