Maximal densities of μ, δ, and κ receptors are differentially altered by focal cerebral ischaemia in the mouse

Abstract

Though opioids are known to have neuroprotective properties, little information is available on the functional state of opioidergic receptors following focal cerebral ischaemia. The present study investigated the evolution of the B max and K d for [ 3H]DAMGO, [ 3H]DADLE, and [ 3H]U69,593, respectively, for the μ, δ, and κ opioidergic receptors after permanent focal cerebral ischaemia in mice. While the various K d were unchanged, μ and δ B max values were precociously decreased in frontoparietal cortices, earlier than κ receptors, reflecting infarct extension with time. The B max values for μ and δ receptors were also altered in non-infarcted tissues, such as tissues at risk (e.g., temporal auditory cortex) and exofocal (e.g., contralateral and non-infarcted) cortices. These results suggest that, in non-infarcted areas, the observed changes reflect functional modifications to focal ischaemia.