Cell-specific expression of Cre recombinase in rat noradrenergic neurons via CRISPR-Cas9 system

Noradrenergic neurons play a crucial role in the functioning of the nervous system. They formed compact small clusters in the central nervous system. To target noradrenergic neurons in combination with viral tracing and achieve cell-type specific functional manipulation using chemogenetic or optogenetic tools, new transgenic animal lines are needed, especially rat models for their advantages in large body size with facilitating easy operation, physiological parameter monitoring, and accommodating complex behavioral and cognitive studies. In this study, we successfully generated a transgenic rat strain capable of expressing Cre recombinase under the control of the dopamine beta-hydroxylase (DBH) gene promoter using the CRISPR-Cas9 system. Our validation process included co-immunostaining with Cre and DBH antibodies, confirming the specific expression of Cre recombinase. Furthermore, stereotaxic injection of a fluorescence-labeled AAV-DIO virus illustrated the precise Cre-loxP-mediated recombination activity in noradrenergic neurons within the locus coeruleus (LC). Through crossbreeding with the LSL-fluorescence reporter rat line, DBH-Cre rats proved instrumental in delineating the position and structure of noradrenergic neuron clusters A1, A2, A6 (LC), and A7 in rats. Additionally, our specific activation of the LC noradrenergic neurons showed effective behavioral readout using chemogenetics of this rat line. Our results underscore the effectiveness and specificity of Cre recombinase in noradrenergic neurons, serving as a robust tool for cell-type specific targeting of small-sized noradrenergic nuclei. This approach enhances our understanding of their anatomical, physiological, and pathological roles, contributing to a more profound comprehension of noradrenergic neuron function in the nervous system.