Accumulation of cyclic nucleotides, blockade of adenosine receptor and translocation of intracellular calcium have received major attention in the mechanism of action of caffeine. These cellular actions of caffeine seems to influence on the levels of biogenic amines in the brain. However, the effect of caffeine on the brain amines is not clear. Present investigation was undertaken to elucidate the effect of caffeine on the regional levels of these amines in rat brain.
The male Sprague-Dawley rats were received caffeine(40 mg/kg,ip). Thirty minutes after caffeine, blocks of tissues were obtained from the frontal cortex, corpus striatum, hippocampus, thalamus, hypothalamus, substantia nigra and cerebellum. The concentration of amines(norepinephrine, dopamine, 5-hydroxytry-ptamine(5-HT)and their metabolites(dihydroxyphenylacetic acid(DOPAC), 5-hydroxyindoleacetic acid(5-HIAA) in brain were detected by employing High Performance Liquid Chromatograph-Electrochemical Dectector.
The results obtained are as follows.
1. In the brain of untreated normal rat, the highest concentration of norepinephrine were found in hypothalamus, that of dopamine and DOPAC in corpus striatum, and that of 5-HT and 5-HIAA in substantia nigra.
2. Caffeine had little effect on the levels of norepinephrine in brain tissues.
3. Caffeine increased the concentration of dopamine in cerebellum and decreased the ratio of DOPAC/Dopamine in coupus striatum.
4. The concentration of 5-HT was little influenced by caffeine, however, the ratio of 4-HIAA / 5-HT was decreased in frontal cortex and substantia nigra.
From the above results, caffeine has little effent on the concentration of the amines in various brain tissues, however, the metabolism of these amines changed significantly by caffeine. Therefore, it is suggested that these metabolic changes of the amines in the brain may by concerned with the behavioral effect of caffeine.
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