Dopaminergic-GABAergic interplay and alcohol binge drinking

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• The dopamine D3 receptor (D3R) in the nucleus accumbens (NAc) is implicated in alcohol reward.
• Medium spiny neurons (MSNs) in the NAc are key targets of dopaminergic input.
• Previous work linked D3R deletion to increased GABA A α6 subunit expression in the ventral striatum.

Purpose of the Study:

• To investigate if D3R-dependent changes in NAc GABA A α6 subunit expression influence voluntary alcohol intake.
• To determine the role of GABA A α6 subunit activity in the NAc on alcohol consumption.
• To elucidate the mechanism by which D3R affects inhibitory transmission in MSNs.

Main Methods:

• Utilized D3 receptor knockout (D3R-/-) and wild-type (D3R+/+) mice for in vivo and ex vivo experiments.
• Employed Ro 15-4513 (α6-GABA A ligand) and furosemide (α6-GABA A antagonist) to probe α6 subunit function.
• Assessed alcohol intake using the drinking-in-the-dark paradigm.
• Measured inhibitory postsynaptic currents in NAc MSNs using whole-cell patch-clamp electrophysiology.
• Quantified α6 subunit expression via in situ hybridization and qPCR.

Main Results:

• NAc α6 subunit expression was significantly higher in D3R-/- mice compared to D3R+/+ mice at baseline.
• Systemic and intra-NAc administration of Ro 15-4513 inhibited alcohol intake in D3R+/+ but increased it in D3R-/- mice.
• Selective α6-GABA A antagonism with furosemide in the NAc increased alcohol intake in D3R-/- mice.
• MSNs in D3R-/- mice exhibited higher miniature inhibitory postsynaptic current amplitudes, which were reduced by Ro 15-4513.
• D3R deletion specifically increased α6 subunit mRNA and protein levels in the NAc.

Conclusions:

• Dopamine D3 receptor signaling negatively regulates the expression of the GABA A α6 subunit in the NAc.
• Enhanced GABA A α6 subunit expression in D3R-/- mice leads to increased inhibitory transmission in NAc MSNs.
• This heightened GABAergic inhibition contributes to reduced voluntary alcohol intake in D3R-/- mice.
• Targeting the D3R-GABA A α6 subunit pathway may offer novel therapeutic strategies for alcohol use disorder.