Targeting Catecholaminergic Systems in Transgenic Rats With a CAV-2 Vector Harboring a Cre-Dependent DREADD Cassette

Juan-Carlos Cerpa,Jean-Rémi Pape,Yoan Salafranque,Etienne Coutureau,Alain R Marchand,Eric J Kremer

doi:10.3389/fnmol.2020.00121

Abstract

Techniques that allow the manipulation of specific neural circuits have greatly increased in the past few years. DREADDs (Designer receptors exclusively activated by designer drugs) provide an elegant way to manipulate individual brain structures and/or neural circuits, including neuromodulatory pathways. Considerable efforts have been made to increase cell-type specificity of DREADD expression while decreasing possible limitations due to multiple viral vectors injections. In line with this, a retrograde canine adenovirus type 2 (CAV-2) vector carrying a Cre-dependent DREADD cassette has been recently developed. In combination with Cre-driver transgenic animals, the vector allows one to target neuromodulatory pathways with cell-type specificity. In the present study, we specifically targeted catecholaminergic pathways by injecting the vector in knock-in rat line containing Cre recombinase cassette under the control of the tyrosine hydroxylase promoter. We assessed the efficacy of infection of the nigrostriatal pathway and the catecholaminergic pathways ascending to the orbitofrontal cortex (OFC) and found cell-type-specific DREADD expression.

Highlights

Elucidation of neural circuits underlying complex animal behaviors depends on tools allowing control of neuronal activity
It has extensively been shown that the substantia nigra pars compacta (SNc) sends major projections to the dorsal striatum (Fallon and Moore, 1978)
The same Figure shows that dopaminergic cells in the ventral tegmental area (VTA), which do not target the dorsolateral striatum (DLS), did not express hM4Di-mCherry

Summary

Introduction

Elucidation of neural circuits underlying complex animal behaviors depends on tools allowing control of neuronal activity. One of the main drawbacks of such a strategy is that it requires two vectors, which obviously increases the likelihood of injections misplacements and raises the problem of the proportion of infected cells To overcome these limitations, we report here a strategy that combines a single CAV-2 vector carrying a Cre-dependent DREADD cassette (CAV-hM4Di) and a Cre driver rat line. We injected CAV-hM4Di in either the DLS or the OFC of TH-cre rats which express Cre-recombinase in dopaminergic and noradrenergic neurons We show that this new CAV-2-based viral vector can and effectively transduce catecholaminergic neurons with both projection and neuronal specificity

Methods

Results

Conclusion