Effect of early-life stress on functional development of raphe-somatosensory neuron-astrocyte network.

2023 Fiscal Year Research-status Report

• Project/Area Number: 23KF0287
• Research Institution: Okinawa Institute of Science and Technology Graduate University
• Principal Investigator: Kuhn Bernd 沖縄科学技術大学院大学, 光学ニューロイメージングユニット, 教授 (90599557)
• Co-Investigator(Kenkyū-buntansha): TEPPOLA-GUREL HEIDI 沖縄科学技術大学院大学, 光学ニューロイメージングユニット, 外国人特別研究員
• Project Period (FY): 2023-11-15 – 2026-03-31
• Keywords: early-life stress / two-photon imaging / astrocytes / layer 5 neurons / calcium imaging / somatosensory cortex / anxiety

Outline of Annual Research Achievements

Preliminary results show that early life stress (ELS) significantly reduces weight gain in mice 21 days after birth. I tested repeatedly during early adulthood. Results from several behavioral studies show a trend that ELS increases anxiety-like behaviour in mice in adulthood. The demanding technique of craniotomy surgeries with viral injections and mounting of a chronical cranial window with access port have been learnt and majority of them have been successful.

The first functional calcium imaging trials with our home built two-photon microscopes of layer 5 pyramidal neurons show that the planned design works, but details need to be finetuned. I was able to image somata and dendrites in awake behaving animals for an extended time repeatedly. Deep imaging was possible with good quality. I was able to record from up to 100 neurons. Imaging data was collected and will now be analyzed.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

I have established an early-life stress (ELS) protocol and breeding of transgenic mice line and exposed half of the bred mice to ELS using limited bedding and nesting combined with maternal separation. I have weighed the control and stress mice on days 4,8,10,12,14,21,28,35 and 42 after birth to investigate weather ELS influences mice weights. Three types of behavioural experiments (open field, light-dark transition, elevated plus maze) have been conducted to measure whether ELS affects anxiety levels in adult mice. I have learnt and performed several craniotomy surgeries on the somatosensory cortex and neuron and astrocyte virus injections in adult mice. I have performed 2-photon microscopy for functional calcium imaging of astrocytes and neurons in awake mice.

Strategy for Future Research Activity

Next, I will perform more craniotomy surgeries and virus injections for all breed transgenic ELS-exposed mice and control mice. In addition, all 40 mice will be subjected to behavioural tests. I am planning to measure plasma corticosterone levels from blood to determine the impacts of ELS on the levels of stress hormone. Additionally, I am planning to measure the restricted diffusion of water in brain tissue to determine structural information of brain tissue with ex vivo diffusion tensor imaging MRI technique from control and early-life stress exposed adult mice. In parallel, I will start analyzing the calcium imaging data.