DECREASE IN BRAIN TISSUE OXYGENATION IN SPITE OF AN INCREASE IN CEREBRAL BLOOD FLOW DURING ACUTE FOCAL 4-AMINOPYRIDINE SEIZURES IN RAT NEOCORTEX
Abstract number :
2.118
Submission category :
Year :
2005
Submission ID :
5422
Source :
www.aesnet.org
Presentation date :
12/3/2005 12:00:00 AM
Published date :
Dec 2, 2005, 06:00 AM
Authors :
1Mingrui Zhao, 1Hongtao Ma, 2Saadat Shariff, 1Danny Wong, 1Minah Suh, and 1Theodore H. Schwartz
Epileptic events elicit an increase in neuronal metabolism and an increase in cerebral blood flow (CBF), bringing oxygenated hemoglobin to the activated neurons. Whether CBF is adequate to meet metabolic demand is unknown. We induced acute focal seizures in rat neocortex by injection of 4-aminopyridine (4-AP, 25mM). The local field potential was recorded to identify the ictal discharge. The partial pressure of tissue oxygen (pO2) and CBF were measured with a Clark-style polarographic oxygen microelectrode and laser Doppler flowmetry. The duration of ictal discharge ranged from 120 to 200 sec (9 seizures, 3 rats). CBF increased to maximum of 131.9[plusmn] 12.8 % of baseline (p[lt]0.05). Tissue pO2 decreased by 64.3[plusmn]7.8 % (p[lt] 0.003) during ictal discharge and increased at the termination of ictal event by 263.6[plusmn]140% (p[lt]0.05). These results demonstrated a prolonged epileptic dip in tissue oxygenation during ictal events in spite of a dramatic increase in CBF. This epileptic ischemia may be responsible for neuronal injury associated with long epileptic events. (Supported by the NIH NS043799-04 and NS049482-01.)