The MCH neuron population as a model for the development and evolution of the lateral and dorsal hypothalamus

• The distribution of MCH neurons is conserved in the posterior dorsal hypothalamus of all vertebrates.
• In mammals, MCH neurons have a precocious phenotypical differentiation.
• Differentiation of MCH phenotypes reflect mechanisms involved in dorsal hypothalamic differentiation in an evo-devo perspective.

The LHA contains neurons producing melanin-concentrating hormone (MCH) or hypocretin (Hcrt) that have emerged as being more conspicuous and representative of the posterior LHA. In this review, we focus on MCH neurons and show that they have unique qualities. Their distribution is conserved in the posterior hypothalamus of all vertebrates and their ontogenetic differentiation is very precocious in the rodent embryo. In mammals, interspecific differences in their medio-lateral distribution suggest that the LHA differentiation may follow species specific strategies. These characteristics make a very valuable tool of MCH neurons to study the development as well as the phylogenetical origin and differentiation of the LHA.