Acute and repeated flibanserin administration in female rats modulates monoamines differentially across brain areas: a microdialysis study.

ABSTRACT

INTRODUCTION: Hypoactive sexual desire disorder (HSDD) is defined as persistent lack of sexual fantasies or desire marked by distress. With a prevalence of 10% it is the most common form of female sexual dysfunction. Recently, the serotonin-1A (5-HT(1A)) receptor agonist and the serotonin-2A (5-HT(2A)) receptor antagonist flibanserin were shown to be safe and efficacious in premenopausal women suffering from HSDD in phase III clinical trials. AIM: The current study aims to assess the effect of flibanserin on neurotransmitters serotonin (5-HT), norepinephrine (NE), dopamine (DA), glutamate, and gamma-aminobutyric acid (GABA) in brain areas associated with sexual behavior. METHODS: Flibanserin was administered to female Wistar rats (280-350 g). Microdialysis probes were stereotactically inserted into the mPFC, NAC, or MPOA, under isoflurane anesthesia. The extracellular levels of neurotransmitters were assessed in freely moving animals, 24 hours after the surgery. MAIN OUTCOME MEASURES: Dialysate levels of DA, NE, and serotonin from medial prefrontal cortex (mPFC), nucleus accumbens (NAC), and hypothalamic medial preoptic area (MPOA) from female rats. RESULTS: Acute flibanserin administration decreased 5-HT and increased NE levels in all tested areas. DA was increased in mPFC and MPOA, but not in the NAC. Basal levels of NE in mPFC and NAC and of DA in mPFC were increased upon repeated flibanserin administration, when compared to vehicle-treated animals. The basal levels of 5-HT were not altered by repeated flibanserin administration, but basal DA and NE levels were increased in the mPFC. Glutamate and GABA levels remained unchanged following either repeated or acute flibanserin treatment. CONCLUSIONS: Systemic administration of flibanserin to female rats differentially affects the monoamine systems of the brain. This may be the mechanistic underpinning of flibanserin's therapeutic efficacy in HSDD, as sexual behavior is controlled by an intricate interplay between stimulatory (catecholaminergic) and inhibitory (serotonergic) systems.