Diffusible factors from rat arcuate nucleus and Broca's diagonal band nucleus increase size and neurite outgrowth, respectively, of cultured melanin-concentrating hormone containing neurons.

Using a co-culture model, we showed that diffusible factors from arcuate nucleus (AN) specifically increased the number and the size of hypothalamic neurons producing melanin-concentrating hormone (MCH). In this model neurite outgrowth and contacts between MCH neurons and dopaminergic neurons were also prominently increased, as compared to control lateral areas of the posterior hypothalamus (LH) primary cultures. These effects were mediated in part by AN glia but also by neurons of both fetal and adult AN. AN glia produced diffusible factor(s) mainly responsible for an important MCH neurite outgrowth and expressed inhibiting factors, preventing the adhesion of LH cells on AN glial cells. Furthermore, we report here a nerve growth factor-like effect from Broca's diagonal band on MCH hypothalamic neurons.