Neurotensin promotes the dendrite elongation and the dendritic spine maturation of the cerebral cortex in vitro

We examined roles of neurotensin in the dendrite formation and the maturation of dendritic spines in the rat cerebral cortex. Embryonic day (E) 18 cortical neurons were cultured for 2 or 4 days in the presence of neurotensin. The chronic treatment of cortical neurons with neurotensin for 4 days increased the dendritic length of non-GABAergic neurons. In addition, the acute treatment of cortical neurons for 24 h at 3 days in vitro also increased the dendritic length of non-GABAergic neurons similarly but more strongly than the chronic treatment. In contrast, the acute treatment for 4 h had no effects on the dendrite formation. Next, we examined the effects of neurotensin on the maturation of dendritic spines. E16 cortical neurons were cultured for 10 or 14 days in a basal medium and then treated with neurotensin for 24 h. At 11 days in vitro, neurotensin increased the postsynaptic density (PSD) 95-positive dendritic protrusions (filopodia, puncta and spines) together with the increase of spine density and the decrease of puncta density. At 15 days in vitro, neurotensin decreased the puncta density. In addition, the immunohistochemical localization of neurotensin type 1 and type 3 receptors in cultured neurons suggested the differential contribution of the receptors in these effects. These findings suggest that neurotensin promotes the dendrite outgrowth and the maturation of dendritic spines of cultured cortical neurons, although further studies are needed to conclude that these roles of neurotensin are also the case in vivo.