Coding the direct/indirect pathways by D1 and D2 receptors is not valid for accumbens projections.

Area of Science:

• Neuroscience
• Dopamine receptor signaling
• Basal ganglia circuitry

Background:

• The basal ganglia play a crucial role in motor control, reward, and motivation.
• Striatal neurons are broadly categorized into D1 dopamine receptor-expressing (direct pathway) and D2 dopamine receptor-expressing (indirect pathway) populations.
• These pathways are traditionally thought to project distinctly to basal ganglia output nuclei.

Purpose of the Study:

• To investigate the projection patterns of D1 and D2 receptor-expressing neurons in the mouse nucleus accumbens to the ventral pallidum.
• To determine if the established direct/indirect pathway architecture in the dorsal striatum applies to the ventral striatum.

Main Methods:

• Utilized a combination of optogenetics and in vivo electrophysiology in mouse models.
• Optogenetic stimulation allowed for targeted activation of specific neuronal populations.
• Electrophysiological recordings measured neuronal activity and projection patterns.

Main Results:

• Contrary to the established model, nucleus accumbens projections to the ventral pallidum did not exhibit strict D1 and D2 receptor-mediated pathway segregation.
• Both D1 and D2 receptor-expressing neurons projected to the ventral pallidum, challenging the concept of exclusive direct and indirect pathways in this region.

Conclusions:

• The traditional model of segregated D1 (direct) and D2 (indirect) pathways originating from the striatum needs re-evaluation for nucleus accumbens projections.
• This study suggests a more complex or overlapping projection architecture in the ventral striatum compared to the dorsal striatum.
• Findings necessitate a reconsideration of dopamine receptor-specific signaling in ventral striatal output pathways.