Brain carbonic acid acidosis after acetazolamide

Area of Science:

• Neuroscience
• Physiology

Background:

• The blood-brain barrier (BBB) regulates the passage of ions and molecules into the brain.
• Understanding how pharmacological agents affect brain pH is crucial for neurological research.

Purpose of the Study:

• To investigate the effects of carbonic anhydrase inhibition on extracellular pH in the feline brain cortex.
• To determine if acetazolamide directly impacts brain tissue pH regulation.

Main Methods:

• Continuous recording of extracellular pH and potassium in the cat brain cortex using implanted microelectrodes.
• Administration of acetazolamide (25 mg/kg) intravenously.
• Assessment of brain pH response to bicarbonate injection, CO2 inhalation, and hyperventilation post-acetazolamide.

Main Results:

• Intravenous acetazolamide induced significant brain acidosis, with a mean pH drop of 0.203 ± 0.046.
• The development of acidosis was slow, suggesting a direct effect on brain tissue.
• Response times to bicarbonate, CO2, and hyperventilation were prolonged after acetazolamide administration.
• No significant changes in extracellular potassium levels were observed.

Conclusions:

• Acetazolamide directly inhibits carbonic anhydrase activity within the brain tissue, leading to acidosis.
• The BBB's integrity was maintained, as evidenced by the development of acidosis following bicarbonate injection.
• Carbonic anhydrase inhibition impacts the brain's pH regulatory mechanisms, affecting responses to physiological challenges.