Central and Peripheral Catecholamine Levels after Pyrazole Treatment

: Pyrazole (50 to 300 mg/kg intraperitoneally) given to male rats produced a decrease in body weight. A dose dependent fall in the noradrenaline content of the brain was observed, but no changes occurred in the central levels of dopamine or 5-hydroxytryptamine. Even a single dose of pyrazole (100 mg/kg) decreased the noradrenaline content by 20 %. Successive doses had an additive effect which was maximal 24 hrs after the final dose. Recovery was quite rapid, but 3 days after the final administration the levels were still lower than in the controls. The noradrenaline content of the heart and spleen was also slightly reduced. The adrenaline content of the adrenals seemed unaffected by the treatment. It is concluded that pyrazole administration in the dose and time schedules used, markedly reduces the noradrenaline content of the central nervous system. This should be kept in mind when this substance is combined with ethanol in similar studies.