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

Lizard diencephalic populations sending axons into the basal plate were stu died by the in vitro HRP technique in the lizard Gallotia. Retrograde label ed cells were concentrated in distinct neuronal groups within alar places o f prosomeres pi and p3, whereas the alar plate of p2 was poorly labeled. Ef ferent fibers from alar pi and p3 populations entered the basal plate of th e diencephalon along topologically dorsoventral courses, bifurcating therea fter into longitudinal ascending (rostral) and descending (caudal) trajecto ries. Thus, diencephalic segments pi and p3 have alar cell populations cont ributing to the longitudinal premotor connectivity of the neural axis, wher eas the alar p2 segment projects via the fasciculus retroflexus, the effere nt tract of the epithalamus. However, the axons from the habenular complex bifurcate within or adjacent to the floor plate and not within the basal pl ate.