DISTRIBUTION OF VIP MESSENGER-RNA AND 2 DISTINCT VIP BINDING-SITES INTHE DEVELOPING RAT-BRAIN - RELATION TO ONTOGENIC EVENTS

The peptide neurotransmitter vasoactive intestinal peptide (VIP) has n eurotrophic properties and influences neurobehavioral development. To assess the role of VIP during neural ontogeny, the present work traces the development of VIP mRNA with in situ hybridization and VIP recept ors with in vitro autoradiography in rat central nervous system (CNS) from embryonic day 14 (E14) to the adult. VIP mRNA was not evident in the CNS until birth. Postnatally, it was expressed in several distinct brain regions, but its distribution bore little relation to that of V IP receptors. VIP receptors were present and expressed changing patter ns of distribution throughout CNS development. The changing patterns w ere the result of 1) the transient appearance of GTP-insensitive VIP r eceptors in several regions undergoing mitosis or glial fasciculation and 2) the transient appearance of GTP-sensitive VIP receptors homogen eously distributed throughout the CNS during the first 2 postnatal wee ks, the period of the brain growth spurt. At E14-16 VIP binding was de nse throughout the brainstem and spinal cord, but limited in the rest of the brain. From E19 to postnatal day 14 (P14), while VIP binding wa s higher in germinal zones, it tended to be uniformly dense throughout the remainder of the brain. By P21 the adult pattern began to emerge; VIP binding was unevenly distributed and was related to specific cyto architectural sites. Since the expression of VIP in the CNS is Limited to postnatal development but VIP receptors are abundant prenatally, w e suggest that extraembryonic VIP may act upon prenatal VIP receptors to regulate ontogenic events in the brain. (C) 1994 Wiley-Liss, Inc.