T. Karasawa, K. Furukawa, K. Yoshida
Nov 25, 1976
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Chemical & pharmaceutical bulletin
Abstract
The effects of 1, 2-benzisoxazole-3-acetamidoxime hydrochloride (PF-257), a novel psychotropic agent possessing the pharmacological properties similar, in some respects, to those of tricyclic antidepressants or monoamine oxidase inhibitors, on the metabolism of brain monoamines were studied in rats. A single large dose or repeated doses of PF-257 caused a slight but significant increase in brain norepinephrine level without affecting the contents of dopamine and serotonin. Like monoamine oxidase inhibitors, PF-257 prevented and reversed the decrease in brain norepinephrine induced by reserpine but it lacked the property to inhibit monoamine oxidase in the brain. Unlike tricyclic antidepressants, the compound was devoid of the capacity to inhibit norepinephrine uptake in vitro. Administration of PF-257 in combination with L-β-3, 4-dihydroxyphenylalanine (L-DOPA) enhanced the increase in brain dopamine without influencing the amount of the amino acid incorporated into the brain. At relatively small doses, PF-257 reduced the rate of decline of brain norepinephrine and dopamine levels following α-methyl-p-tyrosine, a tyrosine hydroxylase inhibitor, and also decreased the levels of brain 3-methoxy-4-hydroxy-phenylethyleneglycol sulfate and homovanillic acid, major metabolites of brain norepinephrine and dopamine, respectively. Thus, it is suggested that the fundamental mechanism underlying the pharmacological and biochemical effects of PF-257 may be its activity to decelerate catecholamine metabolism in the brain without inhibiting the enzymes participating in the metabolic degradation of the amines.