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Stereoselective discriminative stimulus effects of zopiclone in rhesus monkeys.
Psychopharmacology (Berl). 2003 Jan; 165(3):222-8.P

Abstract

RATIONALE

The behavioral effects of racemic zopiclone are similar to those of benzodiazepines that positively modulate GABA at the GABA(A) receptor complex; however, it is not clear how enantiomers or metabolites of zopiclone contribute to the benzodiazepine-like behavioral effects of racemic zopiclone.

OBJECTIVES

Racemic zopiclone, its (R)- and (S)- enantiomers, and the (S)-N-desmethyl metabolite, were evaluated for discriminative stimulus effects in untreated and diazepam treated rhesus monkeys.

METHODS

One group of monkeys discriminated the benzodiazepine midazolam and another group, treated daily with the benzodiazepine diazepam (5.6 mg/kg, PO), discriminated the benzodiazepine antagonist flumazenil.

RESULTS

(RS)-Zopiclone (0.32-17.8 mg/kg) and (S)-zopiclone (0.1-10 mg/kg) substituted with similar potencies for midazolam (>/=80% midazolam-appropriate responding). The midazolam-like discriminative stimulus effects of (RS)-zopiclone were antagonized by flumazenil (p K(B)=7.52). (R)-Zopiclone occasioned a maximum 45% midazolam-appropriate responding at a dose of 100 mg/kg; (S)-desmethylzopiclone produced saline-appropriate responding up to a dose of 100 mg/kg. All four test compounds occasioned predominantly vehicle-appropriate responding in diazepam treated monkeys discriminating flumazenil. (RS)-Zopiclone (10 mg/kg) attenuated the discriminative stimulus effects of flumazenil in diazepam treated monkeys.

CONCLUSIONS

These results clearly demonstrate that in rhesus monkeys the discriminative stimulus effects of zopiclone are stereoselective and qualitatively similar to those of midazolam. These results fail to show any benzodiazepine-like or benzodiazepine antagonist-like discriminative stimulus effects for (S)- N-desmethylzopiclone, suggesting that any behavioral (e.g. anxiolytic) effects of this compound are not the result of actions at benzodiazepine receptors.

Authors+Show Affiliations

Department of Pharmacology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

12434260

Citation

McMahon, Lance R., et al. "Stereoselective Discriminative Stimulus Effects of Zopiclone in Rhesus Monkeys." Psychopharmacology, vol. 165, no. 3, 2003, pp. 222-8.
McMahon LR, Jerussi TP, France CP. Stereoselective discriminative stimulus effects of zopiclone in rhesus monkeys. Psychopharmacology (Berl). 2003;165(3):222-8.
McMahon, L. R., Jerussi, T. P., & France, C. P. (2003). Stereoselective discriminative stimulus effects of zopiclone in rhesus monkeys. Psychopharmacology, 165(3), 222-8.
McMahon LR, Jerussi TP, France CP. Stereoselective Discriminative Stimulus Effects of Zopiclone in Rhesus Monkeys. Psychopharmacology (Berl). 2003;165(3):222-8. PubMed PMID: 12434260.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Stereoselective discriminative stimulus effects of zopiclone in rhesus monkeys. AU - McMahon,Lance R, AU - Jerussi,Thomas P, AU - France,Charles P, Y1 - 2002/11/14/ PY - 2002/04/01/received PY - 2002/09/20/accepted PY - 2002/11/16/pubmed PY - 2003/5/8/medline PY - 2002/11/16/entrez SP - 222 EP - 8 JF - Psychopharmacology JO - Psychopharmacology (Berl) VL - 165 IS - 3 N2 - RATIONALE: The behavioral effects of racemic zopiclone are similar to those of benzodiazepines that positively modulate GABA at the GABA(A) receptor complex; however, it is not clear how enantiomers or metabolites of zopiclone contribute to the benzodiazepine-like behavioral effects of racemic zopiclone. OBJECTIVES: Racemic zopiclone, its (R)- and (S)- enantiomers, and the (S)-N-desmethyl metabolite, were evaluated for discriminative stimulus effects in untreated and diazepam treated rhesus monkeys. METHODS: One group of monkeys discriminated the benzodiazepine midazolam and another group, treated daily with the benzodiazepine diazepam (5.6 mg/kg, PO), discriminated the benzodiazepine antagonist flumazenil. RESULTS: (RS)-Zopiclone (0.32-17.8 mg/kg) and (S)-zopiclone (0.1-10 mg/kg) substituted with similar potencies for midazolam (>/=80% midazolam-appropriate responding). The midazolam-like discriminative stimulus effects of (RS)-zopiclone were antagonized by flumazenil (p K(B)=7.52). (R)-Zopiclone occasioned a maximum 45% midazolam-appropriate responding at a dose of 100 mg/kg; (S)-desmethylzopiclone produced saline-appropriate responding up to a dose of 100 mg/kg. All four test compounds occasioned predominantly vehicle-appropriate responding in diazepam treated monkeys discriminating flumazenil. (RS)-Zopiclone (10 mg/kg) attenuated the discriminative stimulus effects of flumazenil in diazepam treated monkeys. CONCLUSIONS: These results clearly demonstrate that in rhesus monkeys the discriminative stimulus effects of zopiclone are stereoselective and qualitatively similar to those of midazolam. These results fail to show any benzodiazepine-like or benzodiazepine antagonist-like discriminative stimulus effects for (S)- N-desmethylzopiclone, suggesting that any behavioral (e.g. anxiolytic) effects of this compound are not the result of actions at benzodiazepine receptors. SN - 0033-3158 UR - https://www.unboundmedicine.com/medline/citation/12434260/Stereoselective_discriminative_stimulus_effects_of_zopiclone_in_rhesus_monkeys_ L2 - https://dx.doi.org/10.1007/s00213-002-1286-9 DB - PRIME DP - Unbound Medicine ER -