UPTAKE OF EXOGENOUS CAERULEIN IN THE RAT BRAIN: AN IMMUNOHISTOCHEMICAL STUDY

Abstract

A peroxidase-antiperoxidase (PAP) immunohistochemical procedure using a highly specific anti-caerulein antiserum was employed to　investigate the existence and uptake of caerulein in the rat brain. In control rats and in rats that received intramuscular caerulein, no staining was observed. When caerulein was injected into the lateral ventricle, immunoreactive neurons and fibers were observed within 5 min in the cerebral cortex, hippocampus, dentate gyrus, septal area, periventricular regions related to the neuroendocrine system, Purkinje cells, nucleus vestibularis, corpus callosum and fornix. The intensity of immunoreactivity reached its maximum after 15 min; immunoreactivity disappeared within 30 min after the injection. The results indicate that caerulein does not exist physiologically in the rat brain, and that caerulein does not pass the blood-brain barrier. When caerulein is administered intraventricularly, there are some neurons and neuronal fibers which selectively take up caerulein and metabolize it rapidly.