Focal brain lesions induced with ultraviolet irradiation

Mariko Nakata,Shinya Yamamoto,Masayuki Shimoda,Kazuaki Nagasaka,Ichiro Takashima

doi:10.1038/s41598-018-26117-w

Abstract

Lesion and inactivation methods have played important roles in neuroscience studies. However, traditional techniques for creating a brain lesion are highly invasive, and control of lesion size and shape using these techniques is not easy. Here, we developed a novel method for creating a lesion on the cortical surface via 365 nm ultraviolet (UV) irradiation without breaking the dura mater. We demonstrated that 2.0 mWh UV irradiation, but not the same amount of non-UV light irradiation, induced an inverted bell-shaped lesion with neuronal loss and accumulation of glial cells. Moreover, the volume of the UV irradiation-induced lesion depended on the UV light exposure amount. We further succeeded in visualizing the lesioned site in a living animal using magnetic resonance imaging (MRI). Importantly, we also observed using an optical imaging technique that the spread of neural activation evoked by adjacent cortical stimulation disappeared only at the UV-irradiated site. In summary, UV irradiation can induce a focal brain lesion with a stable shape and size in a less invasive manner than traditional lesioning methods. This method is applicable to not only neuroscientific lesion experiments but also studies of the focal brain injury recovery process.

Highlights

Creation of a focal brain lesion has been one of the most fundamental and essential techniques in the field of neuroscience
In contrast to GFAP, Iba-1 immunoreactivity in cells was observed around the lesion and inside the lesion. These findings suggested different roles of these two types of glial cells in tissue subjected to UV irradiation-induced lesioning
We developed a novel experimental method to create a focal brain lesion on the cortical surface by irradiation with UV light

Summary

Introduction

Creation of a focal brain lesion has been one of the most fundamental and essential techniques in the field of neuroscience. A targeted brain site has been destroyed via physical removal of the tissue (e.g., aspiration or cutting with a knife)[1,2,3,4], application of an electrical current[5,6], or injection of drugs[7,8]. These methods are highly invasive; i.e., they require direct access to the targeted site via a needle or an electrode, which breaks membranous tissues covering and protecting the brain (e.g., dura mater). We examined the influence of UV irradiation from an optical fibre placed above the dura and explored the potential of utilizing UV irradiation as a novel experimental technique for creating a focal brain lesion. We further investigated whether size of the UV irradiation-induced brain lesion was controllable, whether the lesion could be visualized in a living animal, and whether generation of a lesion with this technique could disrupt neural activity and neural transmission at the irradiated site

Methods

Results

Conclusion