The connections of the anterior pallium in Pleurodeles waltl and Triturus carnifex: an HRP study.

In order to provide cues about the evolution of the telencephalon in tetrapods, the connections of the anterior pallium were studied in two adult Urodeles, Pleurodeles waltl and Triturus carnifex, by means of the HRP-tracing method. The staining of HRP-immunopositive cell bodies indicates that the pallial regions studied receive afferent projections from the main olfactory bulb and are reciprocally interconnected by intrapallial associative fiber systems. In the ventral hemispheric wall, HRP-immunoreactive perikarya are observed in the pars medialis of the amygdala and in the rostral and caudal striatum. Triturus exhibits a more complex pattern of pallial afferents, including interhemispheric connections and thalamic ascending projections that were not discovered in Pleurodeles. HRP-immunopositive fibers are observed in the dorsal and medial walls of the telencephalon, from the rostral part to the foraminal level. In Triturus, the dorsal fibers extend to the caudal part of the hemisphere. Another group of labelled fibers extends, throughout the lateral and ventral walls, to the most caudal part of the telencephalon, and, through the stria medullaris and the habenular commissure, crosses over to the controlateral hemisphere. These results allow us to specify the basic pattern of the pallial connections in Urodeles and to compare them with data previously obtained in other Amphibians.