Sl. Minger et al., GLUTAMATE-RECEPTOR ANTAGONISTS INHIBIT CALPAIN-MEDIATED CYTOSKELETAL PROTEOLYSIS IN FOCAL CEREBRAL-ISCHEMIA, Brain research, 810(1-2), 1998, pp. 181-199
Excitatory amino acids may promote microtubular proteolysis observed i
n ischemic neuronal degeneration by calcium-mediated activation of cal
pain, a neutral protease. We tested this hypothesis in an animal model
of focal cerebral ischemia without reperfusion. Spontaneously hyperte
nsive rats were treated with dihydroxy-6-nitro-7-sulfamoyl-benzo-(F)qu
inoxaline (NBQX), a competitive antagonist of the neuronal receptor fo
r lpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), or c
is-4-[phosphono-methyl]-2-piperidine carboxylic acid (CGS 19755), a co
mpetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor. Afte
r treatment, all animals were subjected to permanent occlusion of the
middle cerebral artery for 6 or 24 h. Infarct volumes measured in anim
als pretreated with CGS 19755 after 24 h of ischemia were significantl
y smaller than those quantified in ischemic controls. Rats pretreated
with NBQX showed partial amelioration of cytoskeletal injury with pres
erved immunolabeling of microtubule-associated protein 2 (MAP 2) at 6
and 24 h and reduced accumulation of calpain-cleaved spectrin byproduc
ts only at 6 h. Prevention of cytoskeletal damage was more effective a
fter pretreatment with CGS 19755, as shown by retention of MAP 2 immun
olabeling and significant restriction of calpain activity at both 6 an
d 24 h. Preserved immunolabeling of tau protein was observed at 6 and
24 h only in animals pretreated with CGS 19755. Western analysis perfo
rmed on ischemic cortex taken from controls or rats pretreated with ei
ther NBQX or CGS 19755 suggested that loss of tan protein immunoreacti
vity was caused by dephosphorylation, rather than proteolysis. These r
esults demonstrate a crucial link between excitotoxic neurotransmissio
n, microtubular proteolysis, and neuronal degeneration in focal cerebr
al ischemia. (C) 1998 Elsevier Science B.V. All rights reserved.