Recombinase-driver rat lines: tools, techniques, and optogenetic application to dopamine-mediated reinforcement

Area of Science:

• Neuroscience
• Genetics
• Optogenetics

Background:

• Rats are crucial models for neurophysiology and behavior.
• Optogenetic control of specific cell types in rats is currently limited.
• Targeting genetically defined neurons in rats is challenging.

Purpose of the Study:

• To create genetically restricted recombinase-driver rat lines for cell-type-specific gene expression.
• To enable optogenetic manipulation of genetically defined cell populations in rats.
• To investigate the causal role of dopamine neuron activity in reward.

Main Methods:

• Generated Cre recombinase-driver rat lines (e.g., tyrosine hydroxylase [Th]::Cre, choline acetyltransferase [Chat]::Cre) using large regulatory regions.
• Developed methods for optogenetics in freely moving rats.
• Used Th::Cre rats to optically stimulate dopamine neurons in the ventral tegmental area (VTA).

Main Results:

• Achieved specific opsin expression in targeted cell types using the new rat lines.
• Demonstrated the utility of these tools in freely moving rats.
• Showed that optical stimulation of VTA dopamine neurons in Th::Cre rats supports intracranial self-stimulation (ICSS).

Conclusions:

• Established a general approach for optogenetic control of genetically defined cell types in rats.
• Extended the application of optogenetics to traditionally non-genetically-tractable rat models.
• Provided causal evidence linking dopamine neuron firing to positive reinforcement and reward.