Development of an imaging system for in vivo real-time monitoring of neuronal activity in deep brain of free-moving rats

Norio Iijima
Shinji Miyamoto
Keisuke Matsumoto
Ken Takumi
Yoichi Ueta
Hitoshi Ozawa

We have newly developed a system that allows monitoring of the intensity of fluorescent signals from deep brains of rats transgenically modified to express enhanced green fluorescent protein (eGFP) via an optical fiber. One terminal of the optical fiber was connected to a blue semiconductor laser oscillator/green fluorescence detector. The other terminal was inserted into the vicinity of the eGFP-expressing neurons. Since the optical fiber was vulnerable to twisting stresses caused by animal movement
 we also developed a cage in which the floor automatically turns
 in response to the turning of the rat’s head. This relieved the twisting stress on the optical fiber. The system then enabled real-time monitoring of fluorescence in awake and unrestrained rats over many hours. Using this system
 we could continuously monitor eGFP-expression in arginine vasopressin-eGFP transgenic rats. Moreover
 we observed an increase of eGFP-expression in the paraventricular nucleus under salt-loading conditions. We then performed in vivo imaging of eGFP-expressing GnRH neurons in the hypothalamus
 via a bundle consisting of 3000 thin optical fibers. With the combination of the optical fiber bundle connection to the fluorescence microscope
 and the special cage system
 we were able to capture and retain images of eGFP-expressing neurons from free-moving rats. We believe that our newly developed method for monitoring and imaging eGFP-expression in deep brain neurons will be useful for analysis of neuronal functions in awake and unrestrained animals for long durations.

Histochemistry and Cell Biology

Springer Verlag

148

3

10.1007/s00418-017-1576-2

https://doi.org/10.1007/s00418-017-1576-2
https://www.ncbi.nlm.nih.gov/pubmed/28550404