Stereotaxic microinjection of viral vectors expressing Cre recombinase to study the role of target genes in cocaine conditioned place preference

Activity-dependent labeling and manipulation of fentanyl-recruited striatal ensembles using ArcTRAP approach

Understanding the memory substrates underlying substance abuse requires the permanent tagging and manipulation of drug-recruited neural ensembles. Here, we present a protocol for activity-dependent labeling and chemogenetic manipulation of fentanyl-activated striatal ensembles using the ArcTRAP approach. We outline the necessary steps to breed ArcTRAP mice, prepare drugs and reagents, conduct behavioral training, and perform tagging and manipulation. This approach can be adapted to investigate drug-recruited ensembles in other brain regions, providing a versatile tool for exploring the neural mechanisms underlying addiction. For complete details on the use and execution of this protocol, please refer to Wang et al.1.

Stereotaxic Surgery for Genetic Manipulation in Striatal Cells of Neonatal Mouse Brains

Many genes are expressed in embryonic brains, and some of them are continuously expressed in the brain after birth. For such persistently expressed genes, they may function to regulate the developmental process and/or physiological function in neonatal brains. To investigate neurobiological functions of specific genes in the brain, it is essential to inactivate genes in the brain. Here, we describe a simple stereotaxic method to inactivate gene expression in the striatum of transgenic mice at neonatal time windows. AAV-eGFP-Cre viruses were microinjected into the striatum of Ai14 reporter gene mice at postnatal day (P) 2 by stereotaxic brain surgery. The tdTomato reporter gene expression was detected in P14 striatum, suggesting a successful Cre-loxP mediated DNA recombination in AAV-transduced striatal cells. We further validated this technique by microinjecting AAV-eGFP-Cre viruses into P2Foxp2fl/fl mice. Double labeling of GFP and Foxp2 showed that GFP-positive cells lacked Foxp2 immunoreactivity in P9 striatum, suggesting the loss of Foxp2 protein in AAV-eGFP-Cre transduced striatal cells. Taken together, these results demonstrate an effective genetic deletion by stereotaxically microinjected AAV-eGFP-Cre viruses in specific neuronal populations in the neonatal brains of floxed transgenic mice. In conclusion, our stereotaxic technique provides an easy and simple platform for genetic manipulation in neonatal mouse brains. The technique can not only be used to delete genes in specific regions of neonatal brains, but it also can be used to inject pharmacological drugs, neuronal tracers, genetically modified optogenetics and chemogenetics proteins, neuronal activity indicators and other reagents into the striatum of neonatal mouse brains.