Clozapine-N-oxide (CNO) is a metabolite of clozapine, which reduces the density of 5-HT2 receptor in rat primary cortical cells. [1] Clozapine-N-oxide (CNO) also activates an evolved M3-muscarinic receptor and then can be used in chemogenetics. [2]
Clozapine is a known atypical antipsychotic medication used in the treatment of schizophrenia. The two major metabolites of clozapine are norclozapine and clozapine-N-oxide (CNO) [3]. Clozapine is also formed from its N-oxide metabolite. It means that a reversible metabolic pathway exists for clozapine and clozapine-N-oxide (CNO) [4]. In rat primary cortical cells and SHS5Y5 neuroblastoma cells, a significant decrease was found for 5-HT2 receptor density with 200 ng/ml clozapine-N-oxide (CNO) [1]. About the method of identification, reversed-phase HPLC has been reported to detect clozapine and its two major metabolites in human plasma[5].
References:
1. P. Heiser, E. Schulte, C. Hausmann, R. Becker, H. Remschmidt, J. C. Krieg and H. Vedder, Prog Neuropsychopharmacol Biol Psychiatry 2004, 28, 297-302.
2. Armbruster BN1, Li X, Pausch MH, et al. Evolving the lock to fit the key to create a family of G protein-coupled receptors potently activated by an inert ligand. Proc Natl Acad Sci U S A. 2007 Mar 20;104(12):5163-8.
3. S. A. Volpicelli, F. Centorrino, P. R. Puopolo, J. Kando, F. R. Frankenburg, R. J. Baldessarini and J. G. Flood, Clin Chem 1993, 39, 1656-1659.
4. M. W. Jann, Y. W. Lam and W. H. Chang, Arch Int Pharmacodyn Ther 1994, 328, 243-250.
5. A. Avenoso, G. Facciola, G. M. Campo, A. Fazio and E. Spina, J Chromatogr B Biomed Sci Appl 1998, 714, 299-308.