Distribution of enantiomers of trans-tramadol and trans-O-demethyltramadolin central nervous system of rats

Aim: To investigate the distribution of the enantiomers of trans-tramadol ( trans-T) and its active metabolite, trans-O-demethyltramadol (MI), in the c entral nervous system (CNS). Methods: After a single ip dose of trans-T hyd rochloride or Ml, the rats were killed by decapitation. A high performance capillary electrophoresis (HPCE) method was used to determine the concentra tions of enantiomers of trans-T and MI in the serum and different brain tis sues, including cerebrospinal fluid (CF), cerebral cortex (CC), corpus stri atum (CS), hypothalamus (HY), cerebellum (CE), and medulla oblongata (MO). Results: After ip trans-T hydrochloride, the concentrations of (+)-trans-T were higher than those of (-) - trans-T in the serum and all tested brain t issues; The concentrations of (+)-M1 were lower than those of (-)-M1 in the all tested brain tissues; The concentrations of the enantiomers of trans-T and M1 were the highest in the CC, the lowest in the CF. After ip M1, the concentrations of (+)-M1 were higher than those of (-)-M1 in the serum and all tested brain tissues; The concentrations of the enantiomers, of MI were the highest in the CC, the lowest in the CF. Conclusion: The concentration s of the enantiomers of trans-T and MI varied in the serum and different br ain tissues. The distribution of trans-T and M1 in the CNS of rats was ster eoselective. The stereoselectivity in the distribution of M1 after MI injec tion was different with that after trans-T injection.