Induction of Fos expression in the rat brain after intragastric administration of dried bonito .

Dried bonito , a traditional Japanese fish broth made from dried bonito tuna, enhances food palatability due to its specific umami flavor characteristics. However, the pattern of brain activation following ingestion has not been previously investigated. We mapped activation sites of the rat brain after intragastric loads of dried bonito by measuring neuronal levels of the Fos protein, a functional marker of neuronal activation. Compared to intragastric saline, intragastric administration produced enhanced Fos expression in four forebrain regions: the medial preoptic area, subfornical organ, habenular nucleus, and central nucleus of the amygdala. Interestingly, the medial preoptic area was found to be the only feeding-related hypothalamic area responsive to administration. Moreover, had no effect in the nucleus accumbens and ventral tegmental area, two connected sites known to be activated by highly palatable sugars and fats. In the hindbrain, administration produced enhanced Fos expression in both visceral sensory (caudal nucleus of the solitary tract, dorsal part of the lateral parabrachial nucleus, and area postrema) and autonomic (rostral ventrolateral medulla, and caudal ventrolateral medulla) sites. The results demonstrate the activation of discrete forebrain and hindbrain regions following intragastric loads of dried bonito . Our data suggest that the gut-brain axis is the principal mediator of the postingestive effects associated with the ingestion of .