Effect of carbonic anhydrase inhibition on the DC potential difference between cerebrospinal fluid and blood.

The effect of cerebral carbonic anhydrase inhibition on the DC potential difference between cerebrospinal fluid (CSF) and blood (PD) was studied in anesthetized dogs by perfusing the ventriculocisternal system with artificial CSF containing the carbonic anhydrase inhibitor, acetazolamide. The slope of the PD vs. arterial blood pH (delta PD/delta pHa) was calculated from PD and pHa values obtained during room-air breathing, respiratory acidosis, and respiratory alkalosis. delta PD/delta pHa decreased from -26.3 +/- 1.9 millivolts per pH unit (mV/U) before acetazolamide administration to 17.6 +/- 2.1 after acetazolamide (P less than 0.02). The PD at pH 7.4 (PD7.4) increased slightly from 2.9 +/- 0.5 mV before acetazolamide treatment to 3.9 +/- 0.6 after acetazolamide (P less than 0.02). The results suggest that carbonic anhydrase could be involved in generating the PD between CSF and blood.