UPTAKE AND DISTRIBUTION OF FLUORESCEIN-LABELED D-2 DOPAMINE-RECEPTOR ANTISENSE OLIGODEOXYNUCLEOTIDE IN MOUSE-BRAIN

To determine the uptake and distribution of oligodeoxynucleotides in b rain, a 20-mer phosphorothioated oligodeoxynucleotide complementary to a portion of the D-2 dopamine receptor mRNA was fluorescently labeled with fluorescein isothiocyanate (FITC) and injected into the lateral cerebral ventricles of mice. At various survival times after the injec tion, the brains were removed, fixed, sectioned, and viewed under a fl uorescent microscope. The results showed that the oligodeoxynucleotide was rapidly taken up into the brain. Initially the label was relative ly diffusely spread throughout the interstitial spaces of the brain, t hen became redistributed to the cellular compartments. The signal exte nded from those forebrain nuclei located immediately in contact with t he ventricles, such as the corpus striatum, septum, and hippocampus, t o areas further removed from the ventricles, such as the cerebral cort ex, nucleus accumbens, and substantia nigra. When the FITC-labeled D, antisense oligodeoxynucleotide was given once daily for 4 d, the signa l intensity seen 24 h after the last injection appeared to be of great er intensity overall compared to that seen after a single injection. A t early time-points the oligodeoxynucleotide signals appeared to be pu nctuated and were found in cell bodies as well as in proximal dendriti c processes. However, not all cells were equally labeled, suggesting a n uneven uptake and accumulation of the D-2 antisense into the various cell types. At later time-points the fluorescent signal appeared gran ular; at these times the injected material was largely degraded. These studies show that a D-2 dopamine receptor antisense oligodeoxynucleot ide is rapidly taken up from cerebral ventricles into brain, becomes w idely distributed throughout the brain tissue to areas far removed fro m direct contact with the ventricles, and appears to accumulate to a d ifferent extent in the various brain areas and cell types.