Astrocytes are present in large numbers in the nervous system, are associated with synapses, and propagate ionic signals. Astrocytes influence neuronal physiology by responding to and releasing neurotransmitters, but the mechanisms that establish the close interaction between these cells are not defined. Here we use hippocampal neurons in culture to demonstrate that vasoactive intestinal polypeptide (VIP) promotes neuronal differentiation through activity-dependent neurotrophic factor (ADNF), a protein secreted by VIP-stimulated astroglia. ADNF is produced by glial cells and acts directly on neurons to promote glutamate responses and morphological development. ADNF causes secretion of neurotrophin 3 (NT-3), and both proteins regulate NMDA receptor subunit 2A (NR2A) and NR2B. These data suggest that the VIP-ADNF-NT-3 neuronal-glial pathway regulates glutamate responses from an early stage in the synaptic development of excitatory neurons and may also contribute to the known effects of VIP on learning and behavior in the adult nervous system. Key words: glia; synapse; hippocampus; ADNF; NT-3; VIPAn important role for glial cells in synapse function has long been suggested by the intimate relationship that exists between astrocytes and synaptic terminals in vivo (Peters et al., 1991;Ventura and Harris, 1999). Growing evidence indicates that astrocytes play active roles in the CNS (Dani et al., 1992;Porter and McCarthy, 1996). Astrocytes can signal to neurons by releasing soluble factors such as glutamate (Nedergaard, 1994;Parpura et al., 1994) or ␤-chemokines (Brenneman et al., 1999a,b) that regulate neuronal activity (Araque et al., 1998a,b;Meucci et al., 1998). In fact, astrocytes are now viewed as active partners of the presynaptic and postsynaptic terminals in the elaboration of tripartite synaptic structures (Araque et al., 1999). The temporal correlation between glial development and synaptogenesis also suggests an involvement of astrocytes in the formation of the first synapses. In the rat CNS, neurons form most of their synapses during the third postnatal week (Aghajanian and Bloom, 1967), after the differentiation of astrocytes has already been completed (Parnavelas et al., 1983). It has been proposed that glia-derived, soluble factors are necessary for the maturation of developing synapses in vitro (Pfrieger and Barres, 1997). However, the molecular mechanisms that regulate the interactions between neurons and glia are not well defined.Secreted factors such as brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) have been shown to regulate synaptogenesis in the developing hippocampus (Vicario-Abejón et al., 1998), but these factors are neuron-derived proteins that do not require the presence of glia to act on neurons (Song et al., 1997). Among the known regulatory peptides found in the CNS, only vasoactive intestinal polypeptide (VIP) is thought to stimulate glia to generate neurotrophic factors (for review, see Brenneman et al., 1999b). The most potent of these glial signals is the activit...

Periventricular white matter injury (PWMI) is the leading cause of neurodevelopmental morbidity in survivors of premature birth.Cerebral ischemia is considered a major etiologic factor in the generation of PWMI. In adult white matter (WM), ischemic axonal damage is mediated by AMPA/kainate receptors. Mechanisms of ischemic axonal injury during development are not well defined. We used a murine brain slice model to characterize mechanisms of ischemic axonal injury in developing WM. Acute coronal brain slices were prepared from thy1-yellow fluorescent protein (

No abstract

Glucocorticoid hormones exert a variety of effects on the brain and impact memory, anxiety, and CNS responses to stress. The action of these hormones is mediated primarily by soluble receptors, the corticosteroid or glucocorticoid receptors (GRs), which primarily act directly in the nucleus to regulate select networks of target genes. Many in vitro and in vivo model studies have revealed a relationship between expression levels of glucocorticoid receptors and cellular responsiveness to glucocorticoid hormone, particularly in the brain. Various intrinsic and extrinsic factors influence the expression of the glucocorticoid receptors and thereby impact cellular output to glucocorticoid hormone exposure. We had previously shown that the downregulation of GR expression that is characteristic of adult neurons, particular in the hippocampus, does not operate in fetal hippocampal neurons as GR levels are not affected by chronic hormone exposure. This lack of downregulation can be reversed in vitro by the overexpression of a specific E3 ligase for the receptor, carboxyl terminus of hsp70‐interacting protein (CHIP). The impact of CHIP expression in neurons on GR regulated transcription will be examined as well as the pattern of CHIP expression in developing brain, with a particular emphasis on GR responsive regions.