The endocannabinoid system (ECs) is a well known contributor to the hedonic regulation of food intake (FI) in
mammals whereas in fish, the knowledge regarding hedonic mechanisms that control FI is limited. Previous
studies reported the involvement of ECs in FI regulation in fish since anandamide (AEA) treatment induced
enhanced FI and changes of mRNA abundance of appetite-related neuropeptides through cannabinoid receptor 1
(cnr1). However, no previous studies in fish evaluated the impact of palatable food like high-fat diets (HFD) on
mechanisms involved in hedonic regulation of FI including the possible involvement of ECs. Therefore, we aimed
to evaluate the effect of feeding a HFD on the response of ECs in rainbow trout (Oncorhynchus mykiss). First, we
demonstrated a higher intake over 4 days of HFD compared with a control diet (CD). Then, we evaluated the
postprandial response (1, 3 and 6 h) of components of the ECs in plasma, hypothalamus, and telencephalon after
feeding fish with CD and HFD. The results obtained indicate that the increased FI of HFD occurred along with
increased levels of 2-arachidonoylglycerol (2-AG) and AEA in plasma and in brain areas like hypothalamus and
telencephalon putatively involved in hedonic regulation of FI in fish. Decreased mRNA abundance of EC receptors like cnr1, gpr55 and trpv1 suggest a feed-back counter-regulatory mechanism in response to the increased
levels of EC. Furthermore, the results also suggest that neural activity players associated to FI regulation in
mammals as cFOS, γ-Amino butyric acid (GABA) and brain derived neurotrophic factor (BDNF)/neurotrophic
receptor tyrosine kinase (NTRK) systems could be involved in the hedonic eating response to a palatable diet in
fish.Agencia Estatal de Investigación de España | Ref. PID2019-103969RB-C31Xunta de Galicia | Ref. ED431B 2019/37Xunta de Galicia | Ref. ED481A-2019/291Ministerio de Ciencia e Innovación de España | Ref. BES-2017-079708Ministerio de Educación, Cultura y Deporte de España | Ref. FPU16/00045Xunta de Galicia | Ref. ED481B2018/01