We investigated to determine whether dried bonito broth flavor induces a reinforcing effect using the conditioned place preference (CPP) test. Only dried bonito broth did not induce CPP. Sucrose induced CPP in 20% solution. A 21.86% dextrin solution, with the same calorie content as the 20% sucrose solution, did not induce CPP, but a dextrin solution flavored with dried bonito broth (BD) induced CPP. An AD solution containing the same concentrations of dextrin, NaCl, IMP, GMP, and amino acids as found in BD tended to increase the time spent in the conditioned box but did not significantly. Aromatic compounds, such as citral, vanillin, and menthol flavored AD solutions did not induce CPP, whereas an AD solution supplemented with dried bonito flavoring agent induced CPP. In mice with transected olfactory nerves, CPP was not induced by voluntary intake of BD. These results suggest that the aromatic profile of the dried bonito broth plays an important role in BD-induced CPP.

We investigated how gustatory and olfactory information contributes to the preference for dried bonito broth in mice. In the two-bottle preference test, intact mice consumed dried bonito broth in preference to water or an amino acid-nucleotide (AN) solution containing the same concentration of amino acids and nucleotides as that in dried bonito broth. It was observed that mice with transected bilateral chorda tympani (CT) nerves, those with transected bilateral glossopharyngeal (GL) nerves, and those that were intranasally administered with zinc sulfate preferred dried bonito broth to water. Zinc sulfate was used to produce a temporary loss of olfaction. In the two-bottle preference test with dried bonito broth and an AN solution, the preference for the former was reduced in mice with transected bilateral GL nerves and in those with an olfactory blockade, but not in mice with transected bilateral CT nerves. These results suggest that dried bonito broth was preferred over the AN solution, and that simultaneous inputs from olfaction and the GL nerve contributed to this preference.