TRANSIENT EXPRESSION OF NEUROACTIVE SUBSTANCES DURING DEVELOPMENT OF THE CENTRAL-NERVOUS-SYSTEM

Many recent data show that some neuroactive substances are transiently expressed during development and are subsequently reduced or disappea r. These changes are probably due in part to a phenotypic switching or to programmed cell death. This is illustrated for GABA-ergic neurons in the developing brain of Xenopus laevis. Generally, the functional r ole in situ of the transiently expressed neuroactive substances remain s to be elucidated. even though in several cases they may account for some trophic or inductive actions during epigenetic interplays.