Effects of different musical frequencies on NPY and Ghrelin secretion in the rat hypothalamus

It is known that exists a relationship between listening to music and food intake. Hypothalamus appears to integrate the orexigenic properties of a novel peptide, ghrelin (Ghre) that induces food intake through neuropeptide Y (NPY). Ghre stimulates appetite by acting on the ventral hypothalamus, which controls food intake. Ghre is secreted from the stomach and circulates in the bloodstream under fasting conditions, sending a hunger signal from the periphery to the Central Nervous System. The aim of this study was to evaluate, in the rat, the effects of different musical frequencies (432 and 440 Hz) on the Ghre and NPY expression in the hypothalamic neurons through immunohistochemistry; in addition, we investigated on the different production of Ghre in the serum through Western blot assay (Wb), in relation to the body weight of animals. Ghre-immunopositive cells were counted, showing a significant increase in music-treated compared to the control (CTR) group. Similarly, music-treated rats showed increased levels of Ghre in the serum compared to CTR animals. Finally, the body weight of animals was affected by music. In particular, music exposure was able to stimulate the body weight increase and, interestingly, the increase was higher when animals were exposed to music at 440 Hz. Together, the results strongly support the hypothesis that different musical frequencies could affect food intake by modulating the hypothalamic Ghre expression and its release.