The distribution of Dlx1-2 and glutamic acid decarboxylase in the embryonic and adult hypothalamus reveals three differentiated LHA subdivisions in rodents

The lateral hypothalamus (LHA) is still a poorly understood brain region. Based on published Dlx and Gad gene expression patterns in the embryonic and adult hypothalamus respectively, three large areas are identified in the LHA. A central tuberal LHA region is already well described as it contains neurons producing the peptides melanin-concentrating hormone or hypocretin. This region is rich in GABAergic neurons and is specified by Dlx gene expression in the rodent embryo. Rostrally and caudally bordering the tuberal LHA, two Dlx-GAD-GABA poor regions are then easily delineated. The three regions show different organizational schema. The tuberal region is reticularly organized, connected with the cerebral cortex and the spinal cord, and its embryonic development occurs along the tractus postopticus. The region anterior to it is associated with the stria medullaris in both embryonic and adult subjects. The posterior LHA region is made of differentiated nuclei and includes the subthalamic nucleus. Therefore, the LHA is divided into three distinct parts: in addition to the well-known tuberal LHA, caudal and anterior LHA regions exist that have specific anatomical and functional characteristics.