Effects of ischemia on cerebrovascular responses to n-methyl-d
-aspartate in piglets.
Busija, David W., Wei Meng, Ferenc Bari, P. Stephen McGough, Robert A.
Errico, Joseph R. Tobin, and Thomas M. Louis.
Department of Physiology and Pharmacology and Neuroscience Center,
Department of Pediatrics, and Department of Anesthesia and Critical
Care Medicine, Bowman Gray School of Medicine, Wake Forest
University, Winston-Salem, NC 27157; Department of Physiology, Albert
Szent-Gy[diaeresis]orgyi Medical University, Szeged, Hungary;
Department of Anatomy and Cell Biology, East Carolina University,
Greeville, NC 27858
APStracts 2:0436H, 1995.
We examined the effects of total global ischemia on cerebral
arteriolar responses to N-methyl-D-aspartate (NMDA) in anesthetized,
newborn pigs. Arteriolar responses to 10-4M NMDA were determined
before and following 10- or 20-minutes of ischemia caused by
increasing intracranial pressure. Prior to ischemia, NMDA dilated
arterioles by 30+/-5 % (baseline=88+/-2 [mu]m) (n=6). However,
following 10 minutes of ischemia, arteriolar dilation was reduced to
10+/-3% at 1 hour (P<0.05). At 2 and 4 hours, NMDA-induced
dilation was not different from pre-ischemia values. Twenty minutes
of ischemia had similar effects. Coadministration of 100 U/ml of
superoxide dismutase did not restore arteriolar dilation to NMDA at 1
hour following ischemia. Sodium nitroprusside dilated by 14+/-3% and
40+/-5% at 10-6M and 10-5M prior to ischemia, and arteriolar
responsiveness was not changed by ischemia (n=6). Cortical NOS
activity, measured by the in vitro conversion of [14C] arginine to
[14C]citrulline, was unaffected by ischemia (n=12). We conclude that
decreases in cerebral arteriolar responsiveness to NMDA are not due
to impairment of NOS activity, enhanced degradation or chelation of
NO, or to reduced vascular smooth muscle responsiveness to NO.
Received 14 June 1995; accepted in final form 8 September 1995.
APS Manuscript Number H543-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95