Effects of repeated systemic administration of d-Fenfluramine on serotoninand glutamate release in rat ventral hippocampus: comparison with methamphetamine using in vivo microdialysis

We compared the effects of three systemic injections of various doses of d- Fenfluramine, an indirect serotonergic agonist (1.3, 5 or 10 mg/kg), to tho se of a known neurotoxin, methamphetamine (METH, at a 7.5 mg/kg dose), give n i.p. at 2-h intervals, simultaneously on extracellular levels of glutamat e [Glu(ext)] and 5-HT [5-HText] in the ventral hippocampus (VHPC) using in vivo microdialysis in conscious rats. METH markedly increased both [Glu(ext )] (+77% over the control value in saline-treated rats) and [5-HText] (arou nd +250% over controls) in the VHPC. d-Fenfluramine, at all the doses studi ed, induced gradual increases of [5-HText] in the VHPC (between +125% and 417% over control values), but did not modify [Glu(ext)]. These data highli ght marked in vivo differences between METH and d-Fenfluramine in their eff ects on extracellular levels of 5-HT and Glu in the rat ventral hippocampus following their repeated systemic administration.