Re-establishment of direct synaptic connections between sensory axons and motoneurons after lesions of neonatal opossum CNS (Monodelphis domestica) in culture

1998 ◽  
Vol 10 (8) ◽  
pp. 2500-2510 ◽  
Author(s):  
M. Lepre ◽  
J. Fernandéz ◽  
J. G. Nicholls
Keyword(s):  
Monodelphis Domestica ◽  
Synaptic Connections ◽  
Sensory Axons

scholarly journals Pioneer interneurons instruct bilaterality in the Drosophila olfactory sensory map

2019 ◽  
Vol 5 (10) ◽  
pp. eaaw5537 ◽  
Author(s):  
Rashmit Kaur ◽  
Michael Surala ◽  
Sebastian Hoger ◽  
Nicole Grössmann ◽  
Alexandra Grimm ◽  
...  
Keyword(s):  
Cell Adhesion Molecule ◽  
Brain Evolution ◽  
Cellular Interaction ◽  
Synaptic Connections ◽  
Evolutionary Novelty ◽  
Unique Type ◽  
Sensory Axons ◽  
Brain Circuit ◽  
Sensory Map ◽  
Sequential Assembly

Interhemispheric synaptic connections, a prominent feature in animal nervous systems for the rapid exchange and integration of neuronal information, can appear quite suddenly during brain evolution, raising the question about the underlying developmental mechanism. Here, we show in the Drosophila olfactory system that the induction of a bilateral sensory map, an evolutionary novelty in dipteran flies, is mediated by a unique type of commissural pioneer interneurons (cPINs) via the localized activity of the cell adhesion molecule Neuroglian. Differential Neuroglian signaling in cPINs not only prepatterns the olfactory contralateral tracts but also prevents the targeting of ingrowing sensory axons to their ipsilateral synaptic partners. These results identified a sensitive cellular interaction to switch the sequential assembly of diverse neuron types from a unilateral to a bilateral brain circuit organization.

scholarly journals The role of muscle spindles in the development of the monosynaptic stretch reflex

2012 ◽  
Vol 108 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Zhi Wang ◽  
LingYing Li ◽  
Eric Frank
Keyword(s):  
Muscle Fibers ◽  
Muscle Spindles ◽  
Synaptic Connections ◽  
Intrafusal Muscle ◽  
Intrafusal Fibers ◽  
Sensory Axons ◽  
Neurotrophin 3 ◽  
Erbb2 Receptor ◽  
Intrafusal Muscle Fibers

Muscle sensory axons induce the development of specialized intrafusal muscle fibers in muscle spindles during development, but the role that the intrafusal fibers may play in the development of the central projections of these Ia sensory axons is unclear. In the present study, we assessed the influence of intrafusal fibers in muscle spindles on the formation of monosynaptic connections between Ia (muscle spindle) sensory axons and motoneurons (MNs) using two transgenic strains of mice. Deletion of the ErbB2 receptor from developing myotubes disrupts the formation of intrafusal muscle fibers and causes a nearly complete absence of functional synaptic connections between Ia axons and MNs. Monosynaptic connectivity can be fully restored by postnatal administration of neurotrophin-3 (NT-3), and the synaptic connections in NT-3-treated mice are as specific as in wild-type mice. Deletion of the Egr3 transcription factor also impairs the development of intrafusal muscle fibers and disrupts synaptic connectivity between Ia axons and MNs. Postnatal injections of NT-3 restore the normal strengths and specificity of Ia–motoneuronal connections in these mice as well. Severe deficits in intrafusal fiber development, therefore, do not disrupt the establishment of normal, selective patterns of connections between Ia axons and MNs, although these connections require the presence of NT-3, normally supplied by intrafusal fibers, to be functional.

Development of connections by axons growing through injured spinal cord of neonatal opossum in culture

1993 ◽  
Vol 176 (1) ◽  
pp. 77-88
Author(s):  
S. K. Woodward ◽  
J. M. Treherne ◽  
G. W. Knott ◽  
J. Fernandez ◽  
Z. M. Varga ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Molecular Mechanisms ◽  
Light And Electron Microscopy ◽  
Culture Fluid ◽  
Compound Action Potential ◽  
Monodelphis Domestica ◽  
Synaptic Connections ◽  
Small Component ◽  
Entire Central Nervous System

The ability of neurites to grow through a lesion and form synaptic connections has been analyzed in a developing mammalian spinal cord in vitro. After isolation of the entire central nervous system (CNS) of the newly born South American opossum (Monodelphis domestica) the spinal cord was crushed. Outgrowth through and beyond the lesion was observed in living preparations for 2–5 days by staining axons with carbocyanine dyes. The structure of the acute crush and the growing neurites was examined by light and electron microscopy in tissue fixed immediately after the crush had been made. All axons had been severed and the site was filled with debris and amorphous vesicular structures. By 3 days after injury, numerous labelled neurites had grown into the lesion; by 4 days, many had extended several millimetres beyond it. At this time normal axonal profiles were apparent in electron micrographs of the crush site. Although fewer axons grew across the lesion than had been severed by the crush, the amplitudes of compound action potential volleys conducted across the crush in injured preparations were comparable with those recorded from uninjured spinal cords. Physiological experiments made with raised concentrations of extracellular magnesium in the culture fluid indicated that growing axons had formed synaptic connections. Thus, delayed major peaks of the response were abolished while the small component corresponding to through conduction remained unaffected by magnesium. These experiments demonstrate the development of synaptic interactions by the growing neurites and confirm the far greater powers of repair in neonatal mammals compared to adults. They set the stage for comparing molecular mechanisms involved in development and regeneration of the mammalian CNS.

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Inflammational Animal Models for Schizophrenia

2015 ◽  
Vol 223 (3) ◽  
pp. 157-164 ◽  
Author(s):  
Georg Juckel
Keyword(s):  
Animal Model ◽  
Animal Models ◽  
Immune Activation ◽  
Microglial Activation ◽  
Treatment Options ◽  
Early Adulthood ◽  
Brain Regions ◽  
Synaptic Connections ◽  
Preventive Interventions ◽  
Immunological System

Abstract. Inflammational-immunological processes within the pathophysiology of schizophrenia seem to play an important role. Early signals of neurobiological changes in the embryonal phase of brain in later patients with schizophrenia might lead to activation of the immunological system, for example, of cytokines and microglial cells. Microglia then induces – via the neurotoxic activities of these cells as an overreaction – a rarification of synaptic connections in frontal and temporal brain regions, that is, reduction of the neuropil. Promising inflammational animal models for schizophrenia with high validity can be used today to mimic behavioral as well as neurobiological findings in patients, for example, the well-known neurochemical alterations of dopaminergic, glutamatergic, serotonergic, and other neurotransmitter systems. Also the microglial activation can be modeled well within one of this models, that is, the inflammational PolyI:C animal model of schizophrenia, showing a time peak in late adolescence/early adulthood. The exact mechanism, by which activated microglia cells then triggers further neurodegeneration, must now be investigated in broader detail. Thus, these animal models can be used to understand the pathophysiology of schizophrenia better especially concerning the interaction of immune activation, inflammation, and neurodegeneration. This could also lead to the development of anti-inflammational treatment options and of preventive interventions.

Dependence of Sensitive Responses of Chaotic Wandering States on Configuration of Inhibited In-Coming Synaptic Connections

2014 ◽  
Vol 1 ◽  
pp. 644-647 ◽  
Author(s):  
Toshiyuki Hamada ◽  
Jousuke Kuroiwa ◽  
Hisakazu Ogura ◽  
Tomohiro Odaka ◽  
Izumi Suwa ◽  
...  
Keyword(s):  
Synaptic Connections
Sign in / Sign up

Export Citation Format

Share Document