Ultrasound Modulation of Melatonin Release from Pineal Glands In Vitro

Introduction: Previous work has shown that low intensity therapeutic ultrasound releases insulin from human islets and rodent pancreas at increased levels all while retaining cell viability In this study, we aim to determine whether therapeutic ultrasound may stimulate release of sleep-wake hormone, melatonin, from the pineal gland, as well as the safety of this technique. This research could address a significant clinical need by providing a non-invasive method to potentially regulate sleep and circadian rhythms through the targeted release of melatonin.

Materials and

Methods: Rat pineal glands were placed in a well with a KRB solution. Ultrasound was applied to the glands using transducers set at an intensity of 1 W/cm2, and three different frequencies (400, 600, and 800 kHz) with continuous exposure for 5 minutes. Fluid samples were collected from the well before, immediately after, and 30 minutes post-ultrasound treatment. Melatonin release was subsequently measured using an ELISA kit, and analyzed via a Student T test, and Welch’s ANOVA. In addition, histological analysis was completed in order to determine any structural abnormalities. The experimental set-up can be seen in figure one.

Results, Conclusions, and Discussions: All results are shown in figure two. In the sham group, there was a statistically significant 26% increase in melatonin concentration from t=0 min to t=30 min (p ≤0.05) and in the 800 kHz group, there was a statistically significant 56% increase from t=0 min to t=30 min (p ≤0.05). In the 400 kHz and 600 kHz groups there was a non-significant 60% and a 21% decrease respectively from t=0 min to t=30 min (p >0.05). The difference between sham and ultrasound treated groups at 5 min and 30 min was not statistically significant (p >0.05). Additionally, when comparing all groups at each time point (0 min, 5 min, and 30 min) there was a significant difference between the groups at all time points (p ≤0.05). No histological changes were observed in the pineal glands due to ultrasound application. An example of images taken from the histology slides can be seen in figure three. In conclusion, this study indicated that ultrasound may be able to modulate melatonin release in a safe manner. Follow up studies are needed to determine optimal ultrasound parameters for this application.

Acknowledgements (Optional): This work was supported by The George Washington University Cross disciplinary research grant.