Effects of halothane, hypocapnia and hypercapnia on cerebrocortical laser-doppler flow oscillations following inhibition of nitric oxide synthase. Hudetz, Antal G., Jeremy J. Smith, Joseph G. Lee, Zeljko J. Bosnjak and John P. Kampine. Departments of Anesthesiology and Physiology, Medical College of Wisconsin and Zablocki VA Medical Center, Milwaukee, Wisconsin, USA
APStracts 2:0027H, 1995.
We investigated whether nitric oxide (NO) played a role in the generation of cerebrocortical flow oscillations and their modification by hypocapnia, hypercapnia and halothane administration. Parietal cortical laser-Doppler flow (LDF) was monitored transcranially in anesthetized (barbiturate + 0-1.0% halothane), artificially ventilated, adult male Sprague-Dawley rats. Thirty minutes after infusion of L-NAME (20mg/kg, iv.) mean arterial pressure (MAP) increased from 105+10 to 132+15 mmHg (p<0.02) while mean LDF decreased from 159+36 to 135+30 perfusion units (PU, p<0.05). Oscillations in LDF at a frequency of 6.3-7.8cpm and amplitude of 10% were induced or augmented by L-NAME but not by D -NAME or indomethacin (2mg/kg ip.). Sodium nitroprusside infusion (10 -5M, 5-50ml/min) reversed the L-NAME induced increase in MAP and decrease in mean LDF but did not attenuate the flow oscillations. Hypocapnia post L-NAME decreased LDF to 110+20 PU (p<0.001) and augmented the flow oscillations (amplitude: 11-31%). Hypercapnia (5% CO2) or halothane (0.4-1.0%) suspended the oscillations in the presence of L-NAME. The results suggest that NO synthase activity inhibits cerebrocortical flow oscillations but NO is not an obligatory mediator of the effects of halothane, hypocapnia and hypercapnia on oscillatory activity.

Received 18 October 1994; accepted in final form 24 January 1995.
APS Manuscript Number H877-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.