2, Seoul National University, Seoul, , Korea (the Republic of)
Living organisms mainly use nervous and endocrine systems to control the body and maintain homeostasis independently. Endocrinal signal based on the flow of special chemicals called hormone affects the body chronically and massively. When stress is applied to human body, hypothalamus releases corticotropin-releasing hormone (CRH) to the pituitary gland that generates adrenocorticotropic hormone (ACTH) which flows into the adrenal cortex, especially adrenal zona fasciculata (AZF) cell in adrenal gland. The adrenal cortex then produces cortisol, a stress hormone that rebalances body functions and performances of neural and muscular system. However, repeated and chronic stress can cause malfunctions in cortisol releasing endocrine system. Chronic stress involves accumulation of excessive and unnecessary cortisol that eventually cause several diseases such as amnesia, depression, fatigue, anxiety. It is necessary to continuously monitor the cortisol concentration to prevent such diseases which caused by chronic stress. Recently, it was revealed that the electrophysiological (EP) signal induced by ion flux through cellular membrane was responsible for hormone releasing process in corresponded endocrine organs. We assumed that accurate recording of electric signal representing physiological activities of endocrine cells could be applied to characterize cortisol change. Here, we introduce a long lasting, implantable Anchor - like flexible probe that can be used to quantify relationship between cortisol releasing level and electrophysiological (EP) signals from adrenal gland based on flexible EP sensors. This anchor – like probe penetrated through Adrenal Gland, which ensured minimal invasion to organs and stability, low impedance increment over 13 weeks. Through our research, we identified EP signal Frequency was increased in AZF cells, only induced by acute stress or ACTH injection. Thus, our team successfully determined activities of hormonal cells and relative change of cortisol hormone level under stress environment in in vivo animal model. Next, we hypothesized that electrical stimulation of surface of adrenal gland could improve or suppress activity of adrenal gland. We designed elastomer based, conformally attaching stretchable serpentine electrodes. It is known that cortisol secretion is also increased by not only stress but blood loss, therefore we extracted small doses of blood from inferior vena cava (IVC) of rat with every 5 minutes to induce artificial hemmorrhage. By comparing Cortisol concentration of Non - electrical stimulated rat with electrically stimulated showed us that high frequency electrical stimulation tend to suppress activity of AZF cell. However, low frequency electrical stimulation improved AZF cell activity, which showed higher cortisol concentration then standard cortisol concentration. This research of Adrenal gland could provide fundamental knowledge to medical applications such as stress regulator.