A proposed homology between the reptilian dorsomedial thalamic nucleus and the mammalian paraventricular thalamic nucleus.

We have compared the reptilian dorsomedial thalamic nucleus with the mammalian paraventricular thalamic nucleus from a topographic, chemoarchitectonic, and hodological point of view. Both nuclei are localized to a similar position in the dorsalmost aspect of the dorsal thalamus (midline nuclei). They also are uniformly calretinin-immunoreactive, both their cells and neuropil are strongly immunostained for calretinin, and the dorsomedial nucleus presents a strong calbindin immunoreactivity as well. Finally, the reptilian and the mammalian nuclei share a set of afferent and efferent connections with a number of forebrain structures. On the whole, this set of data allows us to propose that the dorsomedial nucleus and the paraventricular thalamic nucleus are homologous. Both represent an important relay station in pathways connecting the hypothalamus with telencephalic areas involved in visceral and motivational aspects of behavior, such as nucleus accumbens and the central amygdala.