Vasopressin: a necessary factor for normal brain development?

The development of selected cerebellar afferents was studied in pouch young opossums using two methods: i) Sternberger's PAP technique for the localization of serotonin; and 2) retrograde transport of horseradish peroxidase (HRP). Serotonin (5HT) immunoreactive elements are present in the rostral cerebellum on postnatal day (PD) i. Between PD 9 and PD 17 there is a sparse, but uniform distr ibution of 5HT posit ive elements in all regions of the developing cerebellum. After PD 30 there is a gradual shift in the distr ibution of 5HT elements unti l PD 37 when the adult pattern is achieved. In the adult, 5HT has its most extensive distr ibution in caudal vermal folia and the paraflocculus. HRP was placed on the cerebellum beginning on PD i0. At this age afferents from the contralateral inferior olive (IO) have reached the cerebellum. A bilateral projection from the basilar pons (BP) as well as from nuclei located dorsal to the pons is present by PD 16. These data suggest that 5HT axons are present in the cerebellum prior to the arrival of efferents from the IO and BP. In addit ion efferents from these precerebellar nuclei reach the cerebellum before their target cells have migrated and matured to form the dist inctive layers characteristic of the adult cerebellum (Laxson and King, '83). (Supported by NS 08798).