Title:Stimulatory and Inhibitory Effect of Antipsychotic Agents Including Dopaminergic Neuro-depressants on Dopamine Formation from p-tyramine Mediated by Cytochrome P450 2D6
Volume: 17
Issue: 1
Author(s): Toshiro Niwa*Yuka Yamamoto
Affiliation:
- School of Pharmacy, Shujitsu University, 1-6-1 Nishigawara, Naka-ku, Okayama, 703-8516, Japan
Keywords:
CYP2D6, dopamine formation, genetic polymorphism, dopaminergic neuro-depressant, haloperidol, sertraline, sulpiride.
Abstract:
Background and Objectives: The effects of antipsychotic agents, including dopamine
D2 receptor blocking agents such as haloperidol, chlorpromazine, and sulpiride, and related
compounds such as mirtazapine and sertraline, on dopamine formation from p-tyramine catalyzed
by cytochrome P450 (CYP) 2D6.2 (Arg296Cys;Ser486Thr), CYP2D6.10
(Pro34Ser;Ser486Thr), and CYP2D6.39 (Ser486Thr) were compared with those of CYP2D6.1.
Methods: Dopamine was determined by high-performance liquid chromatography, and Michaelis
constants (Km), maximal velocity (kcat) values for dopamine formation, and inhibition constants
(Ki) of psychotropic agents were estimated.
Results: Km values for all CYP2D6 variants decreased at lower concentrations, and kcat values
for CYP2D6 variants except for CYP2D6.10 gradually increased with increasing haloperidol
concentrations up to 5 or 10 μM. The kcat/Km values for all CYP2D6 variants increased at under
2.5 μM concentrations. Lower sertraline concentrations decreased Km values for CYP2D6.10.
Chlorpromazine at concentrations under 10 μM competitively inhibited the activities catalyzed
by all variants; however, the activities for only CYP2D6.10 were increased by chlorpromazine at
concentrations over 250 μM. Mirtazapine and sertraline similarly decreased dopamine formation
among all variants except for CYP2D6.10. However, CYP2D6.10 inhibition by mirtazapine was
weaker than that of the other variants, and sertraline decreased Km values for CYP2D6.10.
Conclusion: Haloperidol and sertraline, but not sulpiride, decreased the Km and/or increased kcat
values for CYP2D6. The present findings suggest that Dopamine D2 receptor-blocking agents
and related compounds may polymorphically affect dopamine formation catalyzed by CYP2D6
in the brain.