Comparative Measurement of In Vivo and In Vitro Receptor Binding in the Same Rat Brain

Abstract

Both in vivo and in vitro autoradiograms of 3H-QNB binding in the same rat brain were prepared. The rats were infused with ibotenic acid (20μg/2μL) into the left striatum 14 days prior to the tracer experiment. The rats were intravenously injected with 1.85 MBq of 3H-QNB, and decapitated 60 min later. The frozen sections of brain slices were contacted with imaging plate for 4 weeks, and in vivo autoradiograms were obtained. In vitro autoradiograms of 3H-QNB binding using serial brain slices in the same animal were also made by incubation of 1 nM of 3H-QNB. The influence of residue 3H-QNB in brain slice on in vitro autoradiograms was below 3% of total radioactivity concentration. In the left striatum (ibotenic acid infused side), in vivo binding of 3H-QNB was increased, while in vitro binding in the same region was significantly decreased. By using 3H-labeled ligand, both in vitro and in vivo autoradiograms of receptor binding can be obtained in the same animal. The current method is useful for the study on the discrepancy of receptor binding between in vitro and in vivo.