Inaudible airborne ultrasound affects emotional states in the olfactory bulbectomized rat depression model

Abstract

Recently, exposure to sounds including ultrasound (US) components has been shown to modulate brain activity. However, the detailed US effects on emotional states remain unclear. We previously demonstrated that olfactory bulbectomized (OBX) rats, a widely used depression model are suitable for examining the effects of high-frequency audible sound on emotionality. Here we investigated the impact of inaudible US exposure on the emotional state of OBX rats. Exposure to 100 kHz US for one h did not affect the number of c-Fos-positive cells in auditory-related cortical areas, suggesting that this frequency is inaudible to rats. However, 12- and 24-h exposures to 100 kHz US improved hyperemotionality (HE) scores in OBX rats accompanied by a decrease in the plasma corticosterone levels, suggesting ameliorative effects on depression-like symptoms and stress. In contrast to HE scores, US exposure did not influence anxiety-like behaviors in the elevated plus maze. In conclusion, we demonstrated that exposure to 100 kHz US could alleviate depressive-like symptom in the OBX rat depression model. This is the first study to show that airborne US alone exposure produced the changes in emotional states in animal model. Future research is necessary to elucidate the underlying mechanisms and determine the optimal treatment regimens.