Early neurogenesis in the anterior hypothalamus of the rhesus monkey.

The time of formation of neurons of the various nuclei of the anterior hypothalamus of the rhesus monkey has been determined using [3H]thymidine autoradiography. Plotting of heavily radiolabeled nuclei indicate that in the macaque monkey neurons of the hypothalamus are generated during three weeks, between the 27th and 48th day of the 165 gestational period of this species. The individual nuclei generally display two waves of neuronal generation. Furthermore, a caudolateral to rostromedial gradient of neurogenesis has been observed in the supraoptic nucleus and a dorsal to ventral gradient in the paraventricular nucleus. Thus, neurons of the primate hypothalamus are generated at a much earlier stage of gestation and their generation lasts about three times longer than in rodents. However, most of the basic neurogenetic gradients are remarkably similar, in spite of species specific differences in cytoarchitecture of specific nuclei.