Iomazenil SPECT (BZP-Receptor)

Abstract

123 I-Iomazenil (IMZ) [1] is a specific radioligand for the central benzodiazepine (BZ) receptor that may be useful as an indicator of cortical neuron loss after focal cerebral ischemia using SPECT [2, 3]. The reduction of BZ receptor density in reperfused cortex that remained structurally intact is likely to be the result of injury to only a limited number of neurons (i.e., incomplete brain infarction) [3]. The study of permanent or transient ischemia (lasting 3-6 h) in baboons by Sette et al. [4], who used 18 F-flumazenil as a BZ receptor ligand and PET, has a more direct relevance to the study of the incomplete brain infarction in reperfused cortex using IMZ-SPECT. They observed a decrease of BZ receptor binding not only in the infracted area but also, albeit to a lesser degree, in the CT-intact opercular cortex overlying the hypodense area. Selective neuronal necrosis with sparing of glia and microvessels is seen after transient occlusion of the MCA in macaque monkey and rats [5, 6]. The extent of ischemic neuronal damage depends on both the magnitude and duration of cerebral ischemia. In the study by Garcia et al. [7], up to 60 min of MCA occlusion followed by 7 days of survival in rats resulted in neuronal necrosis that involved isolated groups of cortical neurons (i.e., incomplete brain infarction), while no cases of cortical infarction were found. A close correlation existed between the number of necrotic neurons and the severity of the neurological deficits. © 2010 Springer-Verlag Tokyo.