Voltage-Dependent Dopamine Potency at D₁-Like Dopamine Receptors

Area of Science:

• Neuroscience
• Molecular Pharmacology
• Cellular Electrophysiology

Background:

• Transmembrane voltage influences agonist potency at G protein-coupled receptors (GPCRs).
• Voltage sensitivity of dopamine D2-like receptors is known, but not for D1-like receptors.
• Dopamine D1-like receptors (D1R, D5R) primarily couple to Gαs/olf proteins.

Purpose of the Study:

• To investigate the impact of transmembrane voltage on dopamine potency at D1R and D5R.
• To determine how voltage affects dopamine dissociation rates (koff) at D1R and D5R.
• To elucidate the G protein coupling pathways involved in voltage-dependent dopamine signaling at D1R and D5R.

Main Methods:

• Assay of dopamine potency using GIRK channel activation in Xenopus oocytes co-expressing D1R or D5R at -80 mV and 0 mV.
• Measurement of GIRK response deactivation rates to estimate dopamine dissociation rate (koff) constants.
• Pertussis toxin (PTX) treatment and Gαs antisense oligonucleotide injection to probe G protein involvement.

Main Results:

• Depolarization from -80 mV to 0 mV reduced dopamine potency approximately 7-fold at both D1R and D5R.
• This reduction in potency correlated with increased estimated dopamine koff at both receptors.
• D1R responses were PTX-insensitive, while D5R responses showed significant reduction with PTX treatment and Gαs antisense.

Conclusions:

• Depolarization decreases dopamine affinity at both D1R and D5 receptors.
• Voltage-dependent dopamine affinities at D1R and D5R may play a role in learning and memory.
• D5R signaling involves both Gαs/olf and potentially Gαi/o pathways, influenced by voltage.