Prelimbic cortex 5-HT1A and 5-HT2C receptors are involved in the hypophagic effects caused by fluoxetine in fasted rats

Abstract

The regulation of food intake involves a complex interplay between the central nervous system and the activity of organs involved in energy homeostasis. Besides the hypothalamus, recognized as the center of this regulation, other structures are involved, especially limbic regions such as the ventral medial prefrontal cortex (vMPFC). Monoamines, such as serotonin (5-HT), play an important role in appetite regulation. However, the effect in the vMPFC of the selective serotonin reuptake inhibitor (SSRI), fluoxetine, on food intake has not been studied. The aim of the present study was to study the effects on food intake of fed and fasted rats evoked by fluoxetine injection into the prelimbic cortex (PL), a sub-region of the vMPFC, or given systemically, and which 5-HT receptors in the PL are involved in fluoxetine responses. Fluoxetine was injected into the PL or given systemically in male Wistar rats. Independent groups of rats were pretreated with intra-PL antagonists of 5-HT receptors: 5-HT1A (WAY100635), 5-HT2C (SB242084) or 5-HT1B (SB216641). Fluoxetine (0.1; 1; 3; 10nmol/200nL) injected into the PL induced a dose-dependent hypophagic effect in fasted rats. This effect was reversed by prior local treatment with WAY100635 (1; 10nmol) or SB242084 (1; 10nmol), but not with SB216641 (0.2; 2.5; 10nmol). Systemic fluoxetine induced a hypophagic effect, which was blocked by intra-PL 5-HT2C antagonist (10nmol) administration. Our findings suggest that PL 5-HT neurotransmission modulates the central control of food intake and 5-HT1A and 5-HT2C receptors in the PL could be potential targets for the action of fluoxetine.