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The magnitude and dynamics of [Ca2+] changes in spines and dendrites of hippocampal CA1 pyramidal neurons have been characterized using a low affinity fluorescent indicator, mag-Fura 5, that is sensitive to Ca2+ in the micromolar range. During tetanic stimulation (1 s), we observed progressive [Ca2+] increases in distal CA1 spines to as much as 20-40 μM, both in organotypic slice culture and acute...
Immunoglobulin/fibronectin type III-like cell adhesion molecules have been implicated in axon pathfinding based on their expression pattern in the developing nervous system and on their complex interactions described in vitro. The present in vivo study demonstrates that interactions by two of these molecules, axonin-1 on commissural growth cones and Nr-CAM on floor plate cells, are required for accurate...
We generated mice with a null mutation of the forebrain-restricted transcription factor BF-1 to examine its function in brain development. Heterozygous animals have an apparently normal phenotype. Homozygous null BF-1 mutants die at birth and have a dramatic reduction in the size of the cerebral hemispheres. The development of the ventral telencephalon is more severely affected than that of the dorsal...
The combination of patch-clamp and molecular biology techniques has made it possible to characterize the pharmacological and biophysical properties of ion channels in single neurons and to screen for expression of specific mRNAs in the same cell. Following whole-cell recording, the cytoplasm of the cell is harvested, and RNA is reverse transcribed into cDNA and amplified in PCR with primers specific...
Signaling molecules with either attractive or repulsive effects on specific growth cones are likely to play a role in guiding axons to their appropriate targets. A chick brain glycoprotein, collapsin, has been shown to be a good candidate for a repulsive guidance cue. We report here the discovery of four new molecules related to collapsin in chick brains. All contain a semaphorin domain. One is structurally...
The mechanism of cytoskeletal protein transport, especially the question of what kind of form the cytoskeletal proteins assume during transport in neurons in situ, has been an important, as yet unsettled issue. To clear up this matter, we adopted the embryonic zebrafish as a living animal model and applied the fluorescence recovery after photobleaching (FRAP) method. The zebrafish embryo is appropriate...
Central neurons are subject to a tonic barrage of randomly occurring spontaneous inhibitory events (mIPSCs) resulting from the action potential-independent release of γ-aminobutyric acid (GABA). Do the terminals making synapses onto somatic versus dendritic sites, which arise from specific populations of interneurons, differ in their ability to generate mIPSCs? We have combined the techniques of whole-cell...
The S4 segment comprises part of the voltage sensor in Shaker K+ channels. We have used a strategy similar to intragenic suppression, but without a genetic selection, to identify electrostatic interactions of the S4 segment that may be important in the mechanism of voltage-dependent activation. The S4 neutralization mutations K374Q and R3770 block maturation of the protein, suggesting that they prevent...
In neurons, tubulin is synthesized only in the cell body or dendrites, yet the growing axon requires a steady supply of this protein at the growth cone. Hence, some mechanism must exist to move tubulin from the cell body to the growth cone. Transport could conceivably occur by simple diffusion, translocation of polymer, or some form of monomer or oligomer transport. Evidence for all these has been...
The receptor mechanisms mediating the retrograde axonal transport of the neurotrophins have been investigated in adult rats. We show that transport of the TrkB ligands NT-4 and BDNF to peripheral neurons is dependent on the low affinity neurotrophin receptor (LNR). Pharmacological manipulation of LNR in vivo using either an anti-LNR antibody or a soluble recombinant LNR extracellular domain completely...
Granule cells in the guinea pig dentate gyrus release κ opioid neuropeptides, dynorphins, from dendrites as well as from axon terminals. We have found that both L- and N-type calcium channel antagonists inhibited dendritic dynorphin release. In contrast, N-type but not L-type calcium channel antagonists inhibited axonal dynorphin release. Neither L- nor N-type channel antagonists directly altered...
The CIC family is the superfamily of voltage-gated Cl- channels. Although the CIC channels expressed in Xenopus oocytes have been characterized, their channel properties are still poorly understood. We recently cloned a unique member of the CIC family, CIC-3, that is expressed abundantly in neurons. Its channel activity was regulated by phorbol esters. Now, we have established a stably transfected...
The physiological role of BDNF and NT-3 in the development of the vestibular and auditory systems was investigated in mice that carry a deleted BDNF and/or NT-3 gene. BDNF was the major survival factor for vestibular ganglion neurons, and NT-3, for spiral ganglion neurons. Lack of BDNF and NT-3 did not affect ingrowth of nerve fibers into the vestibular epithelium, but BDNF mutants failed to maintain...
In the developing nervous system, motor axons grow away from the ventral midline floor plate, suggesting that the latter might be a source of repulsive axonal guidance cues. In donorto host transplantation experiments, ectopic pieces of floor plate were positioned between chick hindbrain motor neurons and their exit points. Immunohistochemistry and retrograde axonal labeling techniques demonstrated...
Cell lineage studies of the rat cerebral cortex suggest that by midneurogenesis, most precursor cells of the ventricular zone are specified to produce a single cell type. Yet there is also evidence for multipotential precursor cells. We used a retroviral vector to follow the developmental potential of cortical precursor cells by labeling cortical cells in cultures from embryos between 12 and 18 days...
This paper identifies a neuronal receptor for tenascin-C (tenascin/cytotactin), an extracellular matrix protein that has previously been detected in developing sensory and motor neuron pathways and has been shown to regulate cell migration in the developing CNS. Antibodies specific for each subunit of the integrin asp, are used to demonstrate that α8β1 mediates neurite outgrowth of embryonic sensory...
Restrictions in neuronal fate occur during the transition from a multipotential to a postmitotic cell. This and later steps in neuronal differentiation are determined by extracellular signals. We report that basic fibroblast growth factor is mitogenic for stem cells and is a differentiation factor for calbindin-expressing hippocampal neurons. The neurotrophin NT-3 is a differentiation factor for the...
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