Day/Night Variation of 5-Hydroxyindole Acetic Acid Concentration in Rat Cerebrospinal Fluid After Acute and Long-Term Administration of a Selective Serotonin Reuptake Inhibitor, Fluvoxamine

Abstract

When 30 mg/kg, p.o.of fluvoxamine, a selective serotonin reuptake inhibitor, was administered, significant increases of 3−methoxy−4−hydroxyphenylglycol(MHPG)and 5−hydroxy indole−3−acetic acid(5−HIAA)contents in rat cerebrospinal fluid(CSF)were observed from two days after administration of fluvoxamine in both the light and dark periods and in the dark period of the light/dark cycle, respectively.In long−term treatment with 15 mg/kg, p.o.of fluvoxamine, the level of MHPG in CSF exhibited no difference, whereas the levels of 5−HIAA showed a significant increase during the light periods.These results suggest that fluvoxamine enhances the 5−HT system, but only with long−term treatment.