Effect of short-term oral supplementation with marine-derived n-3 polyunsaturated fatty acids on gene expression of synaptosome-associated protein 25 in the olfactory organ and brain of juvenile chum salmon Oncorhynchus keta

Abstract

In Japan, the release of high-quality hatchery-reared juvenile fish is intended to mitigate against recent declines in adult returns of chum salmon Oncorhynchus keta. One approach to accomplish this aim is through oral supplementation with functional ingredients prior to release of the juveniles. This study aimed to clarify the effect of docosahexaenoic acid (DHA), a marine-derived n-3 polyunsaturated fatty acid (PUFA), on the neural function of juvenile salmon. We examined the messenger RNA (mRNA) expression of synaptosome-associated protein 25 (SNAP25), a molecule related to synaptic vesicle endocytosis, in the brain of hatchery-reared chum salmon juveniles whose feed was supplemented with a DHA-enriched oil for a short period of time. In addition, we tested critical swimming speed to clarify the effect of this supplementation on swimming ability. snap25b expression in the rostral and mid parts of brain was higher in the PUFA-supplemented fish than in the control groups. Both snap25a expression in the mid and caudal parts of brain, including the motor centers, and the results of the swimming ability test were higher in the n-3 PUFA-supplemented group. These findings suggest that short-term oral DHA supplementation in juvenile chum salmon via commercial salmon feed contributes to the enhancement of synaptic plasticity in the central nervous system.