Dennis A. Steindler

Monoclonal antibody to glial fibrillary acidic protein reveals a parcellation of individual barrels in the early postnatal mouse somatosensory cortex

The relative dispositions of cells in immature and mature mouse barrel field cortices that bind antibody to glial fibrillary acidic protein (GFAP) were examined and photographed under the light microscope. Light micrographs demonstrate that radially oriented glial cells are present in the barrel field of postnatal day 6 cortices and that they are located predominantly within the presumptive barrel sides and/or septae, thus sharply delineating individual barrels from each other. The relative dispositions of radial glial fibers observed at this time implicate glia in development of topographic order during early postnatal development of the somatosensory cortex. In contrast, no such delineation could be detected in the cortices of more mature mice, because GFAP-positive astrocytes are present throughout the barrel field and are not confined to barrel sides. This ephemeral nature of the GFAP-delineated barrel field is of interest with respect to the recently reported ephemeral lectin-delineated barrel field.

RT-PCR amplification of mRNA from single brain neurospheres.

A method is described that allows cDNA production from individual brain cell clones or neurospheres. These culture-generated spheres of stem, progenitor, and differentiated cells have been the focus of interest because they represent an in vitro model of neurogenesis. However, because neurospheres are somewhat resistant, in part due to their enclosure by a dense extracellular matrix, to methods attempting to disrupt them and isolate nucleic acids, there is a need for new technology that affords the simple and efficient RT-PCR for studies of neural gene expression and discovery. A method is described here that uses sonication and an all-in-one approach for the construction of cDNA from single neurospheres. The generation of cDNA from individual adult brain stem/progenitor cell neurospheres is useful for future studies of neurogenic gene expression.

The morphology and divergent axonal organization of midbrain raphe projection neurons in the rat

The morphology of dorsal raphe neurons was examined using intracellular injections of horseradish peroxidase (HRP) and the Golgi technique. Light microscopic examination of HRP-labeled projection neurons revealed a neuron type with radiating, poorly branched and sparsely spined dendrites and terminal dendritic thickets. The stem axon of these neurons left the nucleus ventrally but gave off a beaded collateral while still within the parent cells dendritic domain. Somatodendritic morphology from Golgi-Kopsch stained material coincided with intracellular HRP findings and the dorsal raphe may consist of varieties of one basic morphological type of neuron. Intracellular recordings made during the HRP injection experiments confirmed that stimulation of the ventral medial tegmentum elicited an antidromic action potential and an inhibitory postsynaptic potential in dorsal raphe projection neurons. The order of axonal projections arising from the midbrain raphe nuclei was examined using a double retrograde axonal tracing technique. After paired HRP and [3H] wheat germ agglutinin injections within certain projection targets of the dorsal and median raphe neurons (caudate-putamen, amygdala, hippocampus, substantia nigra and locus coeruleus), each target structure was found to have its own unique representation within a topographically distinct portion of one or more of the raphe subgroups. Neurons projecting to the caudate-putamen and substantia nigra occupied rather rostral portions. Neurons projecting to the hippocampus and locus coeruleus resided more caudally. Neurons projecting to the amygdala were situated intermediately. Overall, rostrocaudal topography in the intranuclear distributions of raphe projection neurons resulted in the formation of complex overlap zones where collateralized neurons always resided.

Excess nerve growth factor in the periphery does not obscure development of whisker-related patterns in the rodent brain.

We have addressed the issue of whether or not peripherally expressed nerve growth factor (NGF) influences the formation of whisker‐specific patterns in the brain by regulating the survival of sensory neurons. Transgenic mice that overexpress an NGF cDNA in the skin were examined. In these animals, excess NGF expression is controlled by promoter and enhancer sequences of a keratin gene, thus restricting the higher levels of NGF expression to basal keratinocytes of the epidermis.