MUSIC EFFECT ON WEIGHT, GHRELIN EXPRESSION IN RAT HYPOTHALAMIC NEURONS

Recent studies highlighted that music stimuli play an important role in brain physiology, in some areas related to emotions, food intake and body weight, such as the amygdala, the hippocampus and the hypothalamus. Furthermore, music seems to influence the regulation of the hypothalamic-pituitary-adrenal axis, in the sympathetic nervous system and in the immune system, thus affecting metabolism and energy balance. This leads us to believe that music can have positive effects on the physiological mechanisms directed to metabolic recovery. There are different frequencies to which music can be tuned, today the most used is at 440 Hz, while in the past the 432 Hz frequency was more utilized showing particular effects on brain. Ghrelin (Ghre), a gut-brain peptide hormone, regulates food intake in the hypothalamus; in the last years, it has aroused particular interest for its antioxidant, anti-inflammatory and anti-apoptotic properties. In our previous investigation, we reported that musical stimuli at 432 Hz modified the Ghre expression in the rat, increasing beneficial effects on metabolism. In this study, we used this frequency and we focused our attention on body weight, Ghre expression and neuron morphology in hypothalamic cultures. To investigate the role of music, we utilized newborn pups from pregnant rats; they were divided in two groups: Gr1 without music stimuli, Gr2 with music stimuli at 432 Hz during both the perinatal period and the postnatal period, some for three days (P3) and others for six days (P6). Our results showed that music increased the body weight of pups; in addition, an enhanced Ghre expression in hypothalamic neurons and their axonal elongation were highlighted by immunocytochemical techniques. The expression of Ghre in the ?3- Tubulin positive neurons increased significantly in both Gr1 and Gr2 from P3 to P6. In particular, the increase of the expression of Ghre in the neurons was statistically significant at P3 between Gr1 and Gr2; this increase became highly significant at P6. In addition, the Ghre/?3-Tubulin positive neurons both of Gr1 and Gr2 showed a significant physiological elongation of the processes from P3 to P6. These results suggest that the musical frequency at 432 Hz could stimulate the orexigenic Ghre effects influencing the increase in body weight and affecting the number of hypothalamic neurons expressing Ghre.