5-HT receptors in the ventral tegmental area, but not in the arcuate nucleus, mediate the hypophagic and hypolocomotor effects of the selective 5-HT receptor agonist AR231630 in rats.

Central serotonin systems have long been associated with the control of feeding behavior and the modulation of behavioral effects of psychostimulants. 5-HT receptors are present in hypothalamic centers such as the arcuate nucleus (ARC), controlling homeostatic regulation of food intake, as well as in the ventral tegmental area (VTA), a region involved in motivation aspects in multiple behaviors, including feeding. In the present study, we investigated whether the 5-HT receptors control amphetamine-evoked locomotor activity and regulate food consumption. Localized microinjections into the VTA or the ARC were used to assess the effects of a highly selective 5-HT receptor agonist, AR231630, on the locomotor stimulant effect of amphetamine as well as on food intake. AR231630 injected into the VTA, but not into the ARC, dose-dependently reduced locomotor activity elicited by amphetamine. Unexpectedly, intra-ARC injection of AR231630 did not reduce food intake even at the dose of 10 μg, whereas intra-VTA injection of the same dose of AR231630 did. In addition, we showed that pretreatment with the selective 5-HT receptor antagonist SB242084 infused into the VTA partially prevented hypophagia induced by peripheral administration of AR231630. We can conclude that 5-HT receptor in the VTA, but not in the ARC, participates in both homeostatic and hedonic food intake and brain reward function.