Reelin-expressing neurons in the anterior commissure and corpus callosum of the rat.

Reelin is an extracellular matrix protein, which plays a crucial role for the formation of laminated and nonlaminated structures in the central nervous system. To elucidate its roles in the postnatal brain, in the present study, we raised a polyclonal antibody specific for rat Reelin, and investigated Reelin-expressing neurons in the rat brain during the postnatal periods in detail. We found that some Reelin-expressing cells existed in the anterior commissure and corpus callosum. These Reelin-expressing cells were also immunostained with the antibody specific for neurons, but not immunostained with the antibodies specific for astrocytes nor oligodendrocytes, suggesting that these Reelin-expressing cells in the white matter are neurons. They are also immunostained with anti-GAD67 antibody, indicating that Reelin-expressing cells in the commissure systems are GABAergic neurons. Reelin-expressing neurons in the anterior commissure had many conspicuous varicosities on their dendritic arbors and mimic to the interfascicular neurons. These results suggest that Reelin may participate in the regulatory mechanism of neuronal activities through the commissure structure during the postnatal periods.