TY - JOUR

T1 - Nitric oxide (NO) is an endogenous anticonvulsant but not a mediator of the increase in cerebral blood flow accompanying bicuculline-induced seizures in rats

AU - Wang, Q

AU - Theard, M A

AU - Pelligrino, D A

AU - Baughman, V L

AU - Hoffman, W E

AU - Albrecht, R F

AU - Cwik, M

AU - Paulson, O B

AU - Lassen, N A

PY - 1994/9/26

Y1 - 1994/9/26

N2 - Neurons synthesize NO, which may act as a retrograde messenger, involved in either potentiating or depressing neuronal excitability. NO may also play a role in the cerebral vasodilatory response to increased neuronal activity (i.e., seizures). In this study, two questions were asked: (1) is NO an endogenous anticonvulsant or proconvulsant substance? and (2) is the cerebral blood flow (CBF) increase accompanying bicuculline (BC)-induced seizures mediated by NO? The experiments were performed in 300-400-g Wistar rats anesthetized with 0.6% halothane and 70% N2O/30% O2. CBF was measured using the intracarotid 133Xe clearance method or laser-Doppler flowmetry. EEG activity was recorded. Chronic treatment (4 days) with nitro-L-arginine (L-NA), a potent NO synthase (NOS) inhibitor (400 mg/kg total), suppressed brain NOS by > 97% and prolonged seizure duration from 6 +/- 1 (saline-treated controls) to 12 +/- 2 min. In the L-NA-treated group, the CBF increase was sustained as long as seizure activity remained, indicating that CBF was still tightly coupled to seizure activity. Interestingly, the supposed inactive enantiomer of L-NA, D-NA, also showed an inhibition of brain NOS activity, ranging from 87 to 100%. The duration of seizures in this group (average 8 +/- 2 min) corresponded directly to the magnitude of reduction in NOS activity (r = 0.83, P < 0.05). Specifically, the D-NA results indicated that NOS inhibition had to exceed 95% before any effect on seizure duration could be seen.(ABSTRACT TRUNCATED AT 250 WORDS)

AB - Neurons synthesize NO, which may act as a retrograde messenger, involved in either potentiating or depressing neuronal excitability. NO may also play a role in the cerebral vasodilatory response to increased neuronal activity (i.e., seizures). In this study, two questions were asked: (1) is NO an endogenous anticonvulsant or proconvulsant substance? and (2) is the cerebral blood flow (CBF) increase accompanying bicuculline (BC)-induced seizures mediated by NO? The experiments were performed in 300-400-g Wistar rats anesthetized with 0.6% halothane and 70% N2O/30% O2. CBF was measured using the intracarotid 133Xe clearance method or laser-Doppler flowmetry. EEG activity was recorded. Chronic treatment (4 days) with nitro-L-arginine (L-NA), a potent NO synthase (NOS) inhibitor (400 mg/kg total), suppressed brain NOS by > 97% and prolonged seizure duration from 6 +/- 1 (saline-treated controls) to 12 +/- 2 min. In the L-NA-treated group, the CBF increase was sustained as long as seizure activity remained, indicating that CBF was still tightly coupled to seizure activity. Interestingly, the supposed inactive enantiomer of L-NA, D-NA, also showed an inhibition of brain NOS activity, ranging from 87 to 100%. The duration of seizures in this group (average 8 +/- 2 min) corresponded directly to the magnitude of reduction in NOS activity (r = 0.83, P < 0.05). Specifically, the D-NA results indicated that NOS inhibition had to exceed 95% before any effect on seizure duration could be seen.(ABSTRACT TRUNCATED AT 250 WORDS)

KW - Amino Acid Oxidoreductases/antagonists & inhibitors

KW - Animals

KW - Anticonvulsants/metabolism

KW - Arginine/analogs & derivatives

KW - Bicuculline

KW - Cerebrovascular Circulation/drug effects

KW - Male

KW - Nitric Oxide/physiology

KW - Nitric Oxide Synthase

KW - Nitroarginine

KW - Rats

KW - Rats, Wistar

KW - Seizures/chemically induced

KW - Stereoisomerism

U2 - 10.1016/s0006-8993(09)90026-9

DO - 10.1016/s0006-8993(09)90026-9

M3 - Journal article

C2 - 7530579

VL - 658

SP - 192

EP - 198

JO - Brain Research

JF - Brain Research

SN - 0006-8993

IS - 1-2

ER -