H. Boutin et al., Exofocal alterations in opioidergic receptor densities following focal cerebral ischemia in the mouse, EXP NEUROL, 164(2), 2000, pp. 314-321
In previous studies of our group, we have reported differential alterations
in opioidergic receptor subtypes densities in infarcted and periinfarcted
brain tissue following middle cerebral artery occlusion (MCAO) in mice. Oth
er studies have also described subcortical alterations consecutive to focal
cortical ischemia. For a better understanding of ischemic processes in exo
focal areas, we have investigated the evolution of opioidergic receptors fo
llowing focal cortical ischemia through the quantification of relative bind
ing densities, B-max and K-d values for the mu, delta, and kappa subtypes.
Our results demonstrate that opioid receptor subtypes exhibit adaptations a
t distance from the ischemic core, mainly in the striatum, the thalamus, an
d the substantia nigra. Indeed, mu and delta B-max values were increased in
ventral thalamic nuclei, while kappa relative binding densities were trans
iently increased in nucleus medialis dorsalis and nucleus lateralis, pars p
osterior. Moreover, the B-max of mu and delta receptors were transiently de
creased at 6 h post-MCAO in ipsi- and contralateral patches and matrices of
the striatum. Conversely, the mu B-max values were increased in ipsi- and
contralateral substantia nigra, pars compacta, and pars reticulata, 24 h fo
llowing MCAO. In contralateral substantia nigra, pars compacta, kappa B-max
was found to be decreased at 24 h post-MCAO. These alterations could refle
ct neuronal dysfunction in exofocal brain structures, consecutively to the
degeneration of defined neuroanatomical pathways. Our study indicates that
opioidergic receptors could be used as markers of the neuronal reorganizati
on that take place in subcortical areas following an ischemic insult Of the
brain cortex. (C) 2000 Academic Press.