Monitoring neural activities in the VTA in response to nicotine intake using a novel implantable microimaging device

Measurements of the deep brain area of rodents has been one of the most important methods to study deep brain activities, in part due to limited access of this region. In order to address this problem, we have designed and fabricated an implantable microimaging device for fluorescence imaging in the deep brain of rodents. In this study, we established a new fabrication method of a flat and uniformed fluorescence filter for an implantable microimaging device which obtained higher quality images, and aimed to show the performance of the device in the ventral tegmental area (VTA) of rats. We introduced GCaMP6s in the VTA of rats by adeno-associated viral (AAV) injection. The change in the fluorescence intensity was associated with nicotine administration and was observed by using our custom implantable microimaging device. We showed that nicotine administration significantly affected the excitation of DA neurons in different sub-regions of the VTA, reaching a maximum activation between 6-10 minutes following nicotine exposure, followed by a decrease after 31-35 minutes. Therefore, we believe our implantable microimaging device can potentially be used to monitor the neural activation within the sub-regions of the VTA in response to acute nicotine exposure by using GCaMP.