Life science
Medical & healthcare, Drug development

Development of a fluorescent sensor for real-time
recording of oxytocin dynamics in the brain
Department of Pharmacology, Graduate School of Medicine
Specially Appointed Lecturer Daisuke Ino

https://researchmap.jp/daisukeino?lang=en

Professor Hiroshi Hibino						https://researchmap.jp/hiroshi_hibino?lang=en

Oxytocin (OT), a neuromodulator also known as the ‘happinesshormone,’ plays a key role in our rich emotional experiences andoverall mental and physical health. However, spatio-temporal dynamics of OT in the brain remains elusive, largely due to the lack of
the suitable method for measuring OT with a high sensitivity in theliving brain. Hence, we have developed MTRIAOT, an ultra-sensitive
fluorescent sensor for measuring the extracellular OT level withprecision. By using this innovative tool, we have achieved real-timemeasurements of OT dynamics in the living brain, unraveling theenigma surrounding its functions.

▍ Background & Results

Fig.1 Development of an ultra-sensitive fluorescent OT sensor MTRIAOT.
Schematic illustrating how MTRIAOT works (left). Dose-response curveof MTRIAOT (right).

Acute-stress induced OT response

Fast

Social interaction-induced OT response

・・・

Gradual 1 min

OT concentration

・・・▍ Significance of the research and Future perspective

OT response during daily behaviors

・・・Slow2h

OT concentration

The development of MTRIAOT, an ultra-sensitive fluorescent OT
sensor engineered by our team, has empowered us to engage inreal-time monitoring of OT dynamics within the living brain. While
we conducted several proof-of-concept studies in the mouse brain
utilizing MTRIAOT, a multitude of biological phenomena linked to OT
signaling remain untouched. Given a key role of OT as a moleculeof interest in the treatment of complex mental disorders like autism
spectrum disorders and schizophrenia, our tool holds the potential
to illuminate the underlying causes and propel drug development
for these intractable conditions.

5s

OT concentration

OT plays a crucial role in a wide range of physiological functions
such as mitigation of anxiety and stress, regulation of appetite, andcontrol of metabolism, thereby profoundly influencing our rich dailylives. Moreover, abnormalities in OT have been linked to refractorymental disorders, adding to its significance as a pivotal moleculein therapeutic development. However, previous methods to detectand monitor OT have been limited in their ability to accurately reflect dynamic changes in extracellular OT levels over time. Therefore, fundamental questions such as ‘when,’ ‘where,’ and ‘how’ OT
functions in the brain have remained unresolved.
To address this problem, we developed a fluorescent sensor thatdetects the change in the extracellular OT concentration as a fluorescence readout. By introducing sequential mutations to a chimera protein comprising OT receptors and green fluorescent proteins,
we successfully developed MTRIAOT, an ultra-sensitive fluorescent
OT sensor exhibiting approximately eightfold increase in fluorescence intensity upon OT binding (Figure 1). By using MTRIAOT, weconducted in vivo measurements of OT dynamics in mouse brain
under various experimental conditions. Interestingly, our analysis
revealed that the temporal profiles of OT dynamics in the brain arehighly variable depending on the behavioral context of the animal(Figure 2).

・・・Life science

AbstractFig.2 Measurement of brain OT dynamics with MTRIAOT.
Brain OT responses induced by acute-stress stimulus (left), by socialinteraction (center), and during daily behaviors (right). Our measurements revealed that the temporal profiles of OT signals were highlyvariable and depended on the behavioral context of the mouse.

P a t e n t
Tr e a t i s e

Ino, Daisuke; Tanaka, Yudai; Hibino, Hiroshi et al. A fluorescent sensor for real-time measurement of extracellular oxytocin dynamics in the brain. NatureMethods. 2022, 19 (10), 1286-1294. doi: 10.1038/s41592-022-01597-x

URLK e y w o r d oxytocin, fluorescent sensor, fluorescence imaging