Dopamine-₃ receptor modulates intraocular pressure: implications for glaucoma

Area of Science:

• Ophthalmology
• Neuroscience
• Pharmacology

Background:

• Intraocular pressure (IOP) regulation is crucial for preventing optic neuropathies like glaucoma.
• The dopaminergic system, particularly dopamine D₃ receptors (D₃R), is implicated in various physiological processes, but its role in IOP modulation is not fully understood.

Purpose of the Study:

• To investigate the specific role of the dopamine D₃ receptor (D₃R) in the regulation of intraocular pressure.
• To determine if D₃R activation or antagonism affects IOP in normal and hypertensive conditions.

Main Methods:

• Utilized wild-type (WT) and D₃ receptor knockout (KO D₃R⁻/⁻) mice.
• Administered 7-OH-DPAT (D₃R agonist) and U-99194A (D₃R antagonist) topically.
• Measured intraocular pressure using tonometry under normotensive and steroid-induced ocular hypertensive states.
• Confirmed gene expression via PCR analysis of eye tissues.

Main Results:

• Topical application of 7-OH-DPAT significantly reduced IOP in WT mice, irrespective of baseline pressure.
• The D₃R antagonist U-99194A reversed the IOP-lowering effect of 7-OH-DPAT in WT mice.
• No significant change in IOP was observed in KO D₃R⁻/⁻ mice treated with 7-OH-DPAT.
• PCR confirmed D₃R mRNA expression in WT mice and its absence in KO mice.

Conclusions:

• The dopamine D₃ receptor is identified as a critical modulator of intraocular pressure.
• D₃R activation leads to ocular hypotension, suggesting its therapeutic potential.
• These findings have significant implications for developing novel glaucoma treatments, addressing a leading cause of irreversible blindness.