TY - JOUR
T1 - Nitric oxide scavenging by hemoglobin or nitric oxide synthase inhibition by N-nitro-L-arginine induces cortical spreading ischemia when K+ is increased in the subarachnoid space
AU - Dreier, Jens P.
AU - Körner, Katrin
AU - Ebert, Nathalie
AU - Görner, Astrid
AU - Rubin, Inger
AU - Back, Tobias
AU - Lindauer, Ute
AU - Wolf, Tilo
AU - Villringer, Arno
AU - Einhäupl, Karl Max
AU - Lauritzen, Martin
AU - Dirnagl, Ulrich
PY - 1998/1/1
Y1 - 1998/1/1
N2 - We investigated the combined effect of increased brain topical K+ concentration and reduction of the nitric oxide (NO(·)) level caused by nitric oxide scavenging or nitric oxide synthase (NOS) inhibition on regional cerebral blood flow and subarachnoid direct current (DC) potential. Using thiopental-anesthetized male Wistar rats with a closed cranial window preparation, brain topical superfusion of a combination of the NO(·) scavenger hemoglobin (Hb; 2 mmol/L) and increased K+ concentration in the artificial cerebrospinal fluid ([K+](ACSF)) at 35 mmol/L led to sudden spontaneous transient ischemic events with a decrease of CBF to 14 ± 7% (n = 4) compared with the baseline (100%). The ischemic events lasted for 53 ± 17 minutes and were associated with a negative subarachnoid DC shift of-7.3 ± 0.6 mV of 49 ± 12 minutes' duration. The combination of the NOS inhibitor N- nitro-L-arginine (L-NA, 1 mmol/L) with [K+](ACSF) at 35 mmol/L caused similar spontaneous transient ischemic events in 13 rats. When cortical spreading depression was induced by KCl at a 5-mm distance, a typical cortical spreading hyperemia (CSH) and negative DC shift were measured at the closed cranial window during brain topical superfusion with either physiologic artificial CSF (n = 5), or artificial CSF containing increased [K+](ACSF) at 20 mmol/L (n = 4), [K+](ACSF) at 3 mmol/L combined with L-NA (n = 10), [K+](ACSF) at 10 mmol/L combined with L-NA (five of six animals) or [K+](ACSF) at 3 mmol/L combined with Hb (three of four animals). Cortical spreading depression induced long- lasting transient ischemia instead of CSH, when brain was superfused with either [K+](ACSF) at 20 mmol/L combined with Hb (CBF decrease to 20 ± 20% duration 25 ± 21 minutes, n = 4), or [K+](ACSF) at 20 mmol/L combined with L-NA (n = 19). Transient ischemia induced by NOS inhibition and [K+](ACSF) at 20 mmol/L propagated at a speed of 3.4 ± 0.6 mm/min, indicating cortical spreading ischemia (CSI). Although CSH did not change oxygen free radical production, as measured on-line by in vivo lucigenin-enhanced chemiluminescence, CSI resulted in the typical radical production pattern of ischemia and reperfusion suggestive of brain damage (n = 4). Nimodipine (2 μg/kg body weight/min intravenously) transformed CSI back to CSH (n = 4). Vehicle had no effect on CSI (n = 4). Our data suggest that the combination of decreased NO(·) levels and increased subarachnoid K+ levels induces spreading depression with acute ischemic CBF response. Thus, a disturbed coupling of metabolism and CBF can cause ischemia. We speculate that CSI may be related to delayed ischemic deficits after subarachnoid hemorrhage, a clinical condition in which the release of Hb and K+ from erythrocytes creates a microenvironment similar to the one investigated here.
AB - We investigated the combined effect of increased brain topical K+ concentration and reduction of the nitric oxide (NO(·)) level caused by nitric oxide scavenging or nitric oxide synthase (NOS) inhibition on regional cerebral blood flow and subarachnoid direct current (DC) potential. Using thiopental-anesthetized male Wistar rats with a closed cranial window preparation, brain topical superfusion of a combination of the NO(·) scavenger hemoglobin (Hb; 2 mmol/L) and increased K+ concentration in the artificial cerebrospinal fluid ([K+](ACSF)) at 35 mmol/L led to sudden spontaneous transient ischemic events with a decrease of CBF to 14 ± 7% (n = 4) compared with the baseline (100%). The ischemic events lasted for 53 ± 17 minutes and were associated with a negative subarachnoid DC shift of-7.3 ± 0.6 mV of 49 ± 12 minutes' duration. The combination of the NOS inhibitor N- nitro-L-arginine (L-NA, 1 mmol/L) with [K+](ACSF) at 35 mmol/L caused similar spontaneous transient ischemic events in 13 rats. When cortical spreading depression was induced by KCl at a 5-mm distance, a typical cortical spreading hyperemia (CSH) and negative DC shift were measured at the closed cranial window during brain topical superfusion with either physiologic artificial CSF (n = 5), or artificial CSF containing increased [K+](ACSF) at 20 mmol/L (n = 4), [K+](ACSF) at 3 mmol/L combined with L-NA (n = 10), [K+](ACSF) at 10 mmol/L combined with L-NA (five of six animals) or [K+](ACSF) at 3 mmol/L combined with Hb (three of four animals). Cortical spreading depression induced long- lasting transient ischemia instead of CSH, when brain was superfused with either [K+](ACSF) at 20 mmol/L combined with Hb (CBF decrease to 20 ± 20% duration 25 ± 21 minutes, n = 4), or [K+](ACSF) at 20 mmol/L combined with L-NA (n = 19). Transient ischemia induced by NOS inhibition and [K+](ACSF) at 20 mmol/L propagated at a speed of 3.4 ± 0.6 mm/min, indicating cortical spreading ischemia (CSI). Although CSH did not change oxygen free radical production, as measured on-line by in vivo lucigenin-enhanced chemiluminescence, CSI resulted in the typical radical production pattern of ischemia and reperfusion suggestive of brain damage (n = 4). Nimodipine (2 μg/kg body weight/min intravenously) transformed CSI back to CSH (n = 4). Vehicle had no effect on CSI (n = 4). Our data suggest that the combination of decreased NO(·) levels and increased subarachnoid K+ levels induces spreading depression with acute ischemic CBF response. Thus, a disturbed coupling of metabolism and CBF can cause ischemia. We speculate that CSI may be related to delayed ischemic deficits after subarachnoid hemorrhage, a clinical condition in which the release of Hb and K+ from erythrocytes creates a microenvironment similar to the one investigated here.
KW - Cerebral blood flow
KW - Delayed ischemic deficits
KW - Ischemia
KW - Migraine
KW - Migrainous stroke
KW - Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS)
KW - Nitric oxide
KW - Potassium
KW - Spreading depression
KW - Subarachnoid hemorrhage
KW - Vasospasm
UR - http://www.scopus.com/inward/record.url?scp=0031723199&partnerID=8YFLogxK
U2 - 10.1097/00004647-199809000-00007
DO - 10.1097/00004647-199809000-00007
M3 - Journal article
C2 - 9740101
AN - SCOPUS:0031723199
VL - 18
SP - 978
EP - 990
JO - Journal of Cerebral Blood Flow and Metabolism
JF - Journal of Cerebral Blood Flow and Metabolism
SN - 0271-678X
IS - 9
ER -