Effects of phenytoin on mouse cerebellar 5-hydroxytryptamine and norepinephrine

Concentrations of 5-hydroxytryptamine and norepinephrine in mouse cerebellums have been determined at six time intervals after a single intraperitoneal injection of phenytoin, 20 mg/kg. Compared to controls, where phenytoin diluent was injected two hours before the cerebellums were taken, 5-hydroxytryptamine concentrations were 98%, 122%, 104%, 105%, 112% and 120% at 2, 4, 10, 16, 22, and 28 hours, respectively. At the same times norepinephrine concentrations were 102%, 111%, 116%, 96%, 94% and 120% of the control value. Increases of these brain amines, which are primarily inhibitory within the central nervous system, may be related to the anticonvulsant effect of phenytoin.