局所麻酔薬リドカインの脳内モノアミンとその関連代謝物質に及ぼす影響

抄録

It is known that local anesthetic lidocaine displays diphasic effects, inhibition and stimulation, in a dose-dependent manner on the symptoms in the central nervous system. The purpose of the present study was to investigate whether lidocaine exerts influence on brain monoamine or not. The levels of noradrenaline, 3-methoxy 4-hydroxyphenylglycol, dopamine, 3, 4-dihydroxyphenylacetic acid, homovanillic acid, serotonin and 5-hydroxyindoleacetic acid in the cerebral cortex, hypothalamus, corpus striatum and hippocampus of mice treated with lidocaine. The metabolites were examined using the method of high-performance liquid chromatography with electrochemical detection. The mice were injected subcutaneously with lidocaine at 4,20,40 or 80 ㎎/㎏, and killed 0,5,10 and 60 min after the administration. Next, their brains were removed and divided according to the text. The levels of metabolites of brain monoamine in mice receiving 20 ㎎/㎏ lidocaine showed a significant decrease compared to those in the control group. The levels of metabolites of monoamine in some brain areas of mice receiving 40 ㎎/㎏ lidocaine of a non-convulsant dose showed an increase 60 min after the administration, whereas those in mice receiving 80 ㎎/㎏ lidocaine of a convulsant dose showed a tendency to increase, compared to those in the control group. In the present study, it is clarified that the metabolism of monoamine is inhibited with a non-convulsant dose below 40 ㎎/kg of lidocaine and stimulated with a covulsant dose of 80 mg/㎏ lidocaine, although lidocaine has no influence on the levels of noradrenaline, dopamine and serotonin in mouse brain. Moreover, it is found that the magnitude in metabolism of monoamine shows diphasic pattems, depending on the dosage of lidocaine and the lapsed time after administration.