Localization of chick retinal visinin-like immunoreactivity in the rat forebrain and diencephalon

The present study is an examination, using an indirect immunofluorescence method, of the distribution of visinin, a 24,000 dalton peptide, in the rat forebrain and diencephalon. Immunoreactive structures were localized in the neuronal elements showing an uneven distribution. Immunoreactive neurons were found in the olfactory bulb, anterior olfactory nucleus, cerebral cortex, amygdaloid complex, ventral portion of the nucleus caudatus putamen, septal area, nucleus accumbens, nucleus paratenialis, nucleus rhomboideus, nucleus reuniens, nucleus paraventricularis hypothalami, nucleus supraopticus, nucleus anterior hypothalami, preoptic area, hypothalamic periventricular nucleus, nucleus mammillaris medialis, medial habenular nucleus, zona incerta, nucleus lateralis thalami, nucleus tractus optici and gyrus dentatus. Immunoreactive fibers were observed in the above areas, particularly near the labelled cells, forming fiber plexuses of varying density. In addition, dense plexuses were also seen in the globus pallidus, anteroventral nucleus of the thalamus, substantia nigra and hippocampus. In the former three structures, no labelled cells were present and in the latter, a few scattered neurons were found, indicating that these fibers originate from extrinsic sources.