The effects of chlorpromazine and reserpine on the noradrenaline and adrenaline contents of the frontal cortex, the hypothalamus, the hippocampus and the midbrain were studied in the dog. In control dogs, the catechol amine concentrations were highest in the hypothalamus and lowest in the frontal cortex and the hippocampus. Noradrenaline contents were about seven to nine times as high as those of adrenaline in all the areas. Small doses of chlorpromazine raised the catechol amines in all the areas, the rise being maximum with 5 mg/kg. With increase in the dose of chlorpromazine there was a gradual reversal of the effect and, with 25 mg/kg, there was diminution of noradrenaline content in all the areas except in the hypothalamus. In general, chlorpromazine produced a greater rise in adrenaline than it did of noradrenaline content, and the increase of both amines was very high in the midbrain and the hippocampus compared with the other areas. Reserpine, however, depleted the catechol amine contents of all areas. The depletion was greatest for noradrenaline, an effect quite marked in the midbrain and the frontal cortex. It was concluded that the actions of these two tranquillizers on the catechol amines of dog brain differed both as to site and mechanism.
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