Diencephalic neuronal populations projecting axons into the basal plate in a lizard (Gallotia galloti)

Abstract

Lizard diencephalic populations sending axons into the basal plate were studied by the in vitro HRP technique in the lizard Gallotia. Retrograde labeled cells were concentrated in distinct neuronal groups within alar places of prosomeres pi and p3, whereas the alar plate of p2 was poorly labeled. Efferent fibers from alar pi and p3 populations entered the basal plate of the diencephalon along topologically dorsoventral courses, bifurcating thereafter into longitudinal ascending (rostral) and descending (caudal) trajectories. Thus, diencephalic segments pi and p3 have alar cell populations contributing to the longitudinal premotor connectivity of the neural axis, whereas the alar p2 segment projects via the fasciculus retroflexus, the efferent tract of the epithalamus. However, the axons from the habenular complex bifurcate within or adjacent to the floor plate and not within the basal plate.