[Effects of pentoxifylline on 5-hydroxytryptamine in the mouse brain]

Effects of combined administration of pentoxifylline (PTX) and precursors of 5-hydroxytryptamine (5-HT) on behavior and cerebral contents of 5-hydroxytryptophan (5-HTP), 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) were examined in mice. The intraperitoneal administration of PTX at 100 mg/kg to mice pretreated with pargyline (100 mg/kg, i.p.) significantly increased the frequency of head twitches induced by 5-HTP (25 mg/kg, i.p.), and the effect of PTX was approximately 2 times more potent than that of other methylxanthines. In these mice, the cerebral contents of 5-HTP, 5-HT and 5-HIAA were also elevated significantly. However, PTX itself had no effect to induce head twitch response or to increase the contents of the indoles in mice. When administered in combination with tryptophan (100 mg/kg, i.v.) to pargyline-pretreated mice, PTX (100 mg/kg, i.p.) did not affect the contents of the indoles in the brain. These results suggest that PTX may have an effect to promote transport of exogenous 5-HTP into the neurons, besides the 5-HT turnover-increasing effect common to methylxanthine derivatives.