Comparison of psychic emergence reactions after (+/-)-ketamine and (+)-ketamine in mice.
Ketamine is a racemic mixture containing equal parts of (+)-ketamine and (-)-ketamine. The ketamine enantiomorphs are different in anesthesia and psychic emergence reactions after anesthesia. Therefore, (+)-ketamine was compared with racemic ketamine in a number of randomized studies in volunteers and patients. However, their relations remain controversial. In the present studies, the psychic emergence reactions after injection of (+/-)-ketamine and (+)-ketamine were compared in mice. At equimolar doses, the (+)-isomers elicited episodes of hypnosis nearly 1.4-fold more potent than those of the racemic ketamine. After the administration of equihypnotic doses of (+)-ketamine and (+/-)-ketamine, the posthypnotic stimulation of locomotor activity, stereotype behavior and 5-HT-induced head-twitch response by the (+)-enantiomorph was significantly less intense than that of racemic ketamine. In receptor binding test, (+)-ketamine showed a higher affinity for NMDA receptor than that of (+/-)-ketamine, while (+)-ketamine and (+/-)-ketamine showed no affinity for dopamine D2 and serotonin 5-HT2 receptor. These results suggest that the (+)-ketamine has fewer posthypnotic side effects than (+/-)-ketamine when (+)-ketamine and (+/-)-ketamine were administered at equihypnotic dosages and that dopamine D2 and serotonin 5-HT2 receptor were not involved in the effects of (+)-ketamine and (+/-)-ketamine.
Liu
Jing
J
Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Zhangjiang Hi-Tech Park, Pudong, Shanghai 201203, China.
Ji
Xing-Quan
XQ
Zhu
Xing-Zu
XZ
D000778:Anesthetics, Dissociative / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D006990:Hypnosis; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D044348:Receptors, Serotonin, 5-HT2 / Q000378:metabolism; D012020:Reflex, Abdominal / Q000187:drug effects*; D013237:Stereoisomerism; D013239:Stereotyped Behavior / Q000187:drug effects*
D000778:Anesthetics, Dissociative; D017448:Receptors, Dopamine D2; D044348:Receptors, Serotonin, 5-HT2; D007649:Ketamine