Pimozide Increases a Delayed Rectifier K⁺ Conductance in Chicken Embryo Vestibular Hair Cells

Area of Science:

• Neuropharmacology
• Ototoxicology
• Ion Channel Physiology

Background:

• Pimozide is an antipsychotic used for schizophrenia and Tourette's syndrome.
• It acts as a dopaminergic D2 receptor antagonist and affects voltage-gated Ca2+ and K+ channels.
• Common side effects include dizziness and loss of balance, suggesting potential effects on the vestibular system.

Purpose of the Study:

• To investigate the effect of pimozide on K+ channels in chicken embryo vestibular type-II hair cells.
• To understand the cellular mechanisms underlying pimozide's side effects, particularly those related to balance.
• To explore novel pharmacological actions of pimozide beyond its known dopaminergic antagonism.

Main Methods:

• Patch-clamp whole-cell electrophysiology.
• Recording of K+ currents in isolated type-II vestibular hair cells.
• Application of pimozide at a concentration of 3 μM.

Main Results:

• Pimozide slightly blocked transient outward A-type K+ current.
• Pimozide substantially increased delayed outward rectifying K+ current.
• This resulted in significant hyperpolarization of type-II hair cells and reduced their response to depolarizing stimuli.

Conclusions:

• Pimozide's effects on K+ channels inhibit synaptic transmission in vestibular type-II hair cells.
• These findings provide insights into the mechanisms of pimozide-induced dizziness and balance issues.
• Pimozide's action as a K+ channel opener presents a new perspective for its therapeutic applications.