RESEARCH: Zopiclone (Cyclopyrrolone): A Novel Hypnosedative; Hypnosedation Caused by Zopiclone Does Not Impair Memory‐Learning in Albino Mice

SUMMARY Objectives: To evaluate hypnosedative action of Zopiclone by using animal models for hypnosis and sedation (anxiolysis); and to further evaluate whether this hypnosedation impairs memory-learning in albino mice like conventional hypnosedatives. Methods: For evaluation of hypnosedation, following experiments were performed in albino mice: (1) righting reflex test, (2) pentobarbitone sleeping time potentiation, (3) open field apparatus behavior, and (4) elevated plus maze performance. For evaluation of effects on impairment of memory-learning, elevated plus maze retention test was performed in albino mice. Results: Zopiclone (7.5 mg/kg p.o.) did not inhibit the righting reflex. Significant (P < 0.001) potentiation of pentobarbitone sleeping time and increase in exploration in open field apparatus was observed. Elevated plus maze performance also showed significant (P < 0.01) increase in number of entries to open arm at the same time significant (P < 0.02) increase in time spent in open arm was observed. Elevated plus maze retention test showed significant (P < 0.01) increase in transfer latency on second day of experiment. Conclusions: Zopiclone (7.5 mg/kg p.o.) has selective hypnosedative activity but not CNS-depressant activity similar to BZDs. Hypnosedative action of Zopiclone does not impair memory-learning in albino mice like conventional hypnosedatives.