In mammals gastric infusion of glutamate and other amino acids such as arginine or lysine, activate brain areas related to food intake control through vagal afferent nerves resulting in an anorectic response. In fish, recent studies have demonstrated that an intraperitoneal injection of leucine and valine reduce food intake, while proline has no effects. However, these responses are triggered by the central detection of these amino acids and reflect a post-absorptive response. Therefore, the aim of this study is to analyze in fish possible pre-absorptive effects on food intake through gut-brain axis caused by the presence of these amino acids in the gut or in the oral cavity. Thus, 1 mL/100 g body mass of distilled water alone (control) or containing 40 μmol/mL of leucine, valine, proline or glutamate were administrated orally or intragastrically to five groups of rainbow trout. After 20 minutes, samples of hypothalamus and telencephalon were taken. mRNA abundance of neuropeptides involved in the regulation of food intake (NPY, AgRP, POMC, CART), as well as transcription factors involved in the modulation of these neuropeptides (BSX, FoxO1, CREB) were evaluated. In a second experiment the oral and intragastric administration were repeated with the same solutions to evaluate food intake 2h post-treatment. The results are discussed in the context of metabolic regulation of food intake.