Comparison of psychic emergence reactions after (+/-)-ketamine and (+)-ketamine in mice
by
Liu J, Ji XQ, Zhu XZ.
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.
Life Sci. 2006 Mar 13;78(16):1839-44.

ABSTRACT

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.

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