Kikuko Imamoto

Divergent projections of catecholamine neurons of the locus coeruleus as revealed by fluorescent retrograde double labeling technique

Divergent projections of catecholamine (CA) neurons of the locus coeruleus have been studied by fluorescent retrograde double labeling in conjunction with monoamine histofluorescence technique. The present results indicate that the coerulo-cortical CA system is composed of two types of neurons. A predominant type possesses few divergent axons innervating a restricted region, while the other type projects widely to various areas of the cerebral cortex. The existence of divergent axonal projections of single CA neurons in the locus coeruleus to the cerebellum and the spinal cord, to the frontal cortex and the cerebellum, is also demonstrated.

Cajal-Retzius neurons identified by GABA immunohistochemistry in layer I of the rat cerebral cortex

By means of immunohistochemistry using anti-gamma-aminobutyric acid (GABA) antibodies, characteristic neurons of pyriform, bipolar or pleomorphic shapes, regarded as the Cajal-Retzius (CR) neurons, were clearly demonstrated in layer I of the rat cerebral cortex at the various experimental periods. On embryonic day 15, ovoid neurons only in the marginal zone indicated immunoreactivity for GABA. They gradually extended thick processes often in parallel with the pial surface and formed a dense GABA fiber network in immature layer I during the early postnatal periods. Some GABA neurons seemed to migrate into the underlying layers to settle as nonpyramidal cells. With the expansion of brain volume, GABA neurons relatively diminished and decreased in number. Nevertheless, a small number of GABA neurons did exist as essential CR neurons in layer I even in the adult rats aged 9 months.