Topographical differences of RNA labelling in rat brain after intraventricular administration of labelled RNA precursors

Periventricular penetration and disappearance of ICV Tyr-MIF-1, DAMGO, tyrosine, and albumin

The penetration of four radioiodinated materials-Tyr-MIF-1, DAMGO, tyrosine, and albumin-into the periventricular tissue after ICV injection was studied in rats by film autoradiography. Rates of disappearance from the CNS for the injected compounds were also determined by computer-assisted image analysis of the autoradiographic images. The four materials showed distinct patterns of dispersion from the ventricular system, with Tyr-MIF-1 moving farthest into the parenchyma of the brain and albumin primarily restricted to the ventricular space. The other two compounds, tyrosine and DAMGO, had intermediate values. Tyr-MIF-1 also displayed the fastest rate of removal from the brain, which may represent the ability of the peptide to gain access to sites of saturable transport. By contrast, the exit from the brain of DAMGO was minimal, whereas the efflux of albumin and tyrosine was intermediate. These results show the utility of these methods in the simultaneous measurement of both the patterns of distribution within the CNS and the rates of removal from the CNS of compounds injected into the brain.

Tritiated uridine labeling of the retina: variations among retinal quadrants, and between right and left eyes

We have determined the pattern of RNA labeling (uridine incorporation) in the normal retina of the domestic cat. One eye in each of eight cats was labeled by injecting [3H]uridine into the vitreous cavity. Two of the labeled eyes had the lens and vitreous removed 10 days before labeling. Three additional animals received intravenous (i.v.) injections of [3H]uridine. All animals were injected 4 hr into the light period and fixed 24 hr later; then the retinas were divided into quadrants (ST = superior temporal, SN superior nasal, IT = inferior temporal, and IN = inferior nasal). The ST quadrant contains the area centralis and the SN quadrant the optic nerve head. Autoradiograms were prepared from plastic sections 1 micron thick taken near the centre of each quadrant. In animals receiving intravitreal [3H]uridine, the ganglion cells and the inner and outer nuclear layers (INL; ONL) were heavily labeled; the synaptic layers and the retinal pigment epithelium (RPE) were very lightly labeled. Amacrines were the heaviest labeled cells in the INL; cones were more heavily labeled than rods in the ONL. This finding indicates that amacrines and cone photoreceptors may be synthesizing RNA more actively than other retinal neurons. In animals receiving intravenous [3H]uridine the pattern of labeling was the same as above except that the RPE was heavily labeled. Because cells in the ST quadrant appeared to be more heavily labeled than the same cell types in the other retinal quadrants, silver grains over the ONL in each quadrant were counted as grains micron -2 or grains per rod nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of incorporated [3H]uridine in mouse brain as a function of route of administration

The effect of injection by intracranial and systemic routes on the localization of [3H]uridine incorporated into RNA of mouse brain was quantitated autoradiographically. The pattern of labeled RNA 45 min after intraventricular or intracisternal injection was highly variable throughout the brain, and activity was localized in structures adjacent to the ventricles or subarachnoid space. The amount incorporated was inversely related to distance from these cerebrospinal fluid compartments with little incorporation observed at distances greater than 200 microns. In contrast to intracranial administration, intrapleural and subcutaneous routes yielded a more homogeneous distribution of incorporated uridine throughout the brain. Regional differences in the autoradiographic pattern following systemic administration were correlated with regional differences in cell density. The results clearly indicate that injection route is a potent factor affecting the localization of agents used to study brain.