Insulin immunohistochemistry of rodent CNS: apparent species differences but good correlation with radioimmunological data.

Using an indirect immunofluorescence technique the distribution of insulin was mapped in brains of Wistar strain rats and mice. Insulin immunoreactivity was found to be widely distributed throughout mouse CNS, whereas in rat brain a restriction of immunoreactive material to cerebral blood vessels and ependymal cells and/or tanycytes of the brain ventricles was observed. In radioimmunological studies the amount of insulin (IRI) was estimated for different brain areas (cerebral cortex, brain stem, cerebellum, hippocampus, thalamus and hypothalamus). In the case of Wistar rats very low levels of IRI were found. On the contrary, the same regions in mouse brain contained considerably greater amounts of IRI. The comparison between histochemical and biochemical data revealed a good correlation. It is concluded that part of the insulin measured by radioimmunoassay is associated with neuronal structures.