Effects of DHA-Enriched Fish Oil Supplements on Dopamine Receptor Gene Expression in the Cerebral Cortex and Hippocampus Related to the Male Rats Weight Gain

Background: Docosahexaenoic acid (DHA) can penetrate through the barrier between the blood and the brain through simple diffusion and obtains benefits for neurons. Supplementation of DHA-enriched fish oil for seven weeks in young male Wistar rat could alter dopamine (DA) receptor modulation, and it may be related to the increased weight gain. Aim: This present study aims to explore the alteration of the dopamine receptors (D1DR and D2DR) gene expression in the cerebral cortex and hippocampal area, as a top-down circuit control, related to the role of body weight gain as an indicator of food intake. Methods: Twenty samples of Rattus novergicus, aged 7-8 weeks, were randomly grouped into two groups as follows: 10 rats as the control group (CG) and 10 rats in the group that received treatment with fish oil - omega 3 capsules (FOG). CG and FOG were fed with standard laboratory food and received water ad libitum. The treated group (FOG) received 0.2 ml added supplementation of DHA-enrich fish oil (FO) capsules with the daily dose of 30 mg EPA and 45 mg of DHA for 7 weeks via gavage every morning. The body weight of each rat was weighed and recorded every 2 weeks. Results: The weight had increased significantly in the FOG during the first 4 weeks of treatment and continued to grow until the end of the 7 weeks of treatment (p=0.036). The relative D1DR gene expression in the cerebral cortex was significantly higher compared to the relative expression mRNA in the hippocampus region (D1DR 1.6 fold, p <0.05). It was similar to D2DR FOG (p<0.05, 1.1 fold increase compare FOG in HC). Conclusion: Supplementation of DHA-enriched fish oil caused an alteration of the D1DR and D2DR gene expression, as neural circuitry regulating eating correlated with the altering weight gain in young rats with healthy feeding. Keywords: DHA, D1DR, D2DR, Weight gain.