Effect of dried bonito (katsuobushi) and some of its components on GABAA receptors

Katsuobushi, a popular Japanese food additive and traditional flavour enhancer, is produced from a fish, bonito, by a variety of processes, including boiling, sun drying, smoking and mould culturing. Aqueous katsuobushi (AK), which is produced from katsuobushi powder by extraction with water, and some of its aroma components, such as 2-ethyl-3-methylpyrazine and phenol derivatives, potentiated dose-dependently the response of the GABAA receptors expressed in Xenopus oocytes. When AK, 2-ethyl-3-methylpyrazine or 3-methoxyphenol were injected into mice prior to an intraperitoneal administration of pentobarbital, the pentobarbital-induced sleeping time increased. In an elevated plus maze test, intraperitoneal administration of 2-ethyl-3-methylpyrazine to mice increased significantly both the number of entries into the open arms and the duration of stay in the open arms, indicating anti-anxiety activity. Katsuobushi and its aroma components may modulate human mood or consciousness through acting on GABAA receptors in the brain.