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POSSIBLE PARTICIPATION OF NMDA AND GLYCINE RECEPTORS BUT NOT GABA A RECEPTORS IN ENFLURANE‐INDUCED OPISTHOTONUS IN MICE
Author(s) -
Komatsu Hisao,
Nogaya Junko,
Ueki Masaaki,
Yokono Satoshi,
Ogli Kenji
Publication year - 1994
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1994.tb02546.x
Subject(s) - enflurane , strychnine , dizocilpine , pentylenetetrazol , nmda receptor , antagonist , glycine receptor , chemistry , pharmacology , picrotoxin , ketamine , medicine , endocrinology , anesthesia , glycine , receptor , anticonvulsant , biochemistry , halothane , amino acid , psychiatry , epilepsy
SUMMARY 1. We previously reported that volatile anaesthetics produce incidences of a transient opisthotonus in mice, a sign of CNS stimulation. This study was performed to investigate mechanisms by which enflurane‐induced opisthotonus (EIO) occurs. 2. The effects of pretreatment of N ‐methyl‐d‐aspartate (NMDA) antagonists dizocilpine (MK‐801; DIZ) and ketamine (KET), GABA A antagonists picrotoxin (PIC), pentylenetetrazol (PTZ) and glycine antagonist strychnine (STR) on the incidence of EIO were determined. Prior to exposure to 2.0% enflurane in air, male ddN mice were given intraperitoneal injections of 0.2 mL saline (control), 0.5–5.0 mg/kg DIZ, 20–80 mg/kg KET, 2.9 mg/kg PIC, 40.0 mg/kg PTZ and 0.75 mg/kg STR. After the injection, the behavioural state of the mice was observed for 20 min (the pre‐enflurane period). During the exposure to enflurane the time for immobilization, that is, anaesthetic induction time (IT), and the incidence of EIO were measured. 3. Dizocilpine (1.0–5.0 mg/kg) and KET (80 mg/kg) significantly (P<0.01) reduced both the incidence of EIO and IT in a dose‐dependent manner. During the pre‐enflurane period DIZ produced incidences (5–40%) of transient seizures in a dose‐dependent manner, while KET did not induce them at all. The two GABA a antagonists had no detectable effect on the EIO. Strychnine significantly enhanced the EIO. These CNS stimulants resulted in a 3–10% incidence of transient seizure and/or opisthotonus during the pre‐enflurane period, but there was no correlation between DIZ‐induced seizure and EIO. 4. These results suggest that the EIO is mediated by the NMDA and the STR‐sensitive glycine receptors, but not the GABA A receptor. We speculate that DIZ acts on the NMDA‐receptor and/or disrupts the balance between the inhibitory and the excitatory systems.