Nitric oxide modulates cerebral blood flow stimulation by acetazolamide inthe rat cortex: a laser Doppler scanning study

The involvement of nitric oxide (NO) in cerebral blood flow (CBF) stimulati on by acetazolamide was studied in anaesthetised, mechanically ventilated W istar rats. CBF was monitored by laser Doppler scanning. Acetazolamide indu ced a long-lasting significant rCBF-increase. Application of NG-Nitro-L-arg inine (L-NNA), an inhibitor of all NO synthetases (NOS), prevented CBF stim ulation by acetazolamide. Continuous infusion of the exogenous NO donor SIN -1 (3-morpholinosydnonimine) suppressed L-NNA induced increases of mean art erial blood pressure without effect on rCBF in comparison to baseline. Addi tional acetazolamide injection then again caused a significant increase of rCBF in spite of NOS-inhibition. We thus conclude that NO is involved in ac etazolamide-induced CBF stimulation. The mere continuous presence of NO is sufficient to re-establish the acetazolamide-response in spite of NOS-inhib ition. These data suggest that NO acts rather as a modulator than as a medi ator of the acetazolamide-induced CBF response. (C) 2001 Elsevier Science I reland Ltd. All rights reserved.