Tracing of specific neural pathways in the rat brain using lentiviral vectors for retrograde gene transfer

Understanding the structural and the functional organization of neural circuits in the brain is a fundamental goal of neuroscience. Lentiviral vectors for retrograde gene transfer transduce neurons through the entry from synaptic terminals and enable tracing and manipulation of neuronal populations of interests based on the synaptic connections. The highly efficient and neuron-specific retrograde gene transfer (NeuRet) vectors are derived from the pseudotyping of human immunodeficiency virus type 1-based vectors with fusion envelope glycoproteins. Viral RNA genome is reverse-transcribed and synthesized DNA is integrated into the host genomes, allowing stable and long-term expression of transgenes. Dorsal striatum, the input layer of the basal ganglia, integrates signals from various brain regions, including cerebral cortex, thalamus, and ventral midbrain, and plays a critical role in motor control, learning, and decision-making. Consequently, understanding the input and the output connectivity of the dorsal striatum is fundamental to revealing how circuits within the basal ganglia contribute to physiological and behavioral functions, and its impairments are related to neurological disorders. This paper outlines the procedures for injecting a NeuRet vector carrying a green fluorescent protein gene into the sub-regions of dorsal striatum in rats, followed by immunohistochemistry to detect the transgene expression in the brain.