Developmental changes of acetylcholinesterase and pseudocholinesterase in organotypic cultures of spinal cord

High-throughput screening for myelination promoting compounds using human stem cell-derived oligodendrocyte progenitor cells

Promoting myelination capacity of endogenous oligodendrocyte precursor cells (OPCs) is a promising therapeutic approach for CNS demyelinating disorders such as Multiple Sclerosis (MS). To aid in the discovery of myelination-promoting compounds, we generated a genome-engineered human pluripotent stem cell (hPSC) line that consists of three reporters: identification-and-purification tag, GFP, and secreted-NanoLuc, driven by the endogenous PDGFRA, PLP1, and MBP genes, respectively. Using this cell line, we established a high-throughput drug screening platform and performed a small-molecule screen, which identified at least two myelination-promoting small-molecule (Ro1138452 and SR2211) that target prostacyclin (IP) receptor and retinoic acid receptor-related orphan receptor γ (RORγ), respectively. Single-cell-transcriptomic analysis of differentiating OPCs treated with these molecules further confirmed that they promote oligodendrocyte differentiation and revealed several pathways that are potentially modulated by them. The molecules and their target pathways provide promising targets for the possible development of remyelination-based therapy for MS and other demyelinating disorders.

Canadian Pioneers of Amyotrophic Lateral Sclerosis: A Brief History

This is an historical account of Canadian pioneers working in amyotrophic lateral sclerosis (ALS) in the 1970s and 1980s. Key contributions included the development of specialized clinics, the ALS Society of Canada, human motor unit estimates in vivo, use of transcranial magnetic stimulation (TMS), the dementias of ALS, the importance of neurofilaments and axonal flow, neuroinflammation and immunity related to ALS, use of tissue culture to study pathogenesis, and the story of ALS in Guam. Their work set the stage for future generations of ALS physicians and scientists to bring about meaningful therapies and hopefully a cure for ALS.

Cholinergic signaling in myelination

There is a long history of research on acetylcholine (ACh) function in myelinating glia, but a resurgence of interest recently as a result of the therapeutic potential of manipulating ACh signaling to promote remyelination, and the broader interest in neurotransmitter signaling in activity-dependent myelination. Myelinating glia express all the major types of muscarinic and nicotinic ACh receptors at different stages of development, and acetylcholinesterase and butyrylcholinesterase are highly expressed in white matter. This review traces the history of research on ACh signaling in Schwann cells, oligodendrocytes, and in the myelin sheath, and summarizes current knowledge on the intracellular signaling and functional consequences of ACh signaling in myelinating glia. Implications of ACh in diseases, such as Alzheimer's disease, multiple sclerosis, and white matter toxicity caused by pesticides are considered, together with an outline of major questions for future research. GLIA 2017;65:687-698.

Evidence for the existence of alpha- and beta-adrenoceptors on cultured glial cells--an electrophysiological study

The action of adrenergic alpha- and beta-agonists and antagonists has been studied on the membrane potential and resistance of glial cells of cultured rat central nervous system. Noradrenaline and the alpha-adrenoceptor stimulating agents phenylephrine and clonidine (10(-7) to 10(-4)M) depolarized the glial membrane, whereas the beta-agonist isoprenaline caused a hyperpolarization at low concentrations (10(-7) and 10(-6)M). The effects of noradrenaline and phenylephrine were reversibly blocked by the alpha-antagonist phentolamine, whereas those of isoprenaline were antagonized by the beta-blocker atenolol. Atenolol did not affect the depolarization by noradrenaline. The glial depolarization induced by the alpha-agonists was not the consequence of a change in the extracellular K+-concentration unlike that produced by amino acid transmitters. The present results, together with those of biochemical and autoradiographic binding studies, suggest that alpha- and beta-adrenoceptors occur on glial cells and that the glial depolarization is mediated by alpha-receptors, whereas the hyperpolarization is due to activation of beta-receptors.

Evidence for the existence of alpha- and beta-adrenoceptors on neurones and glial cells of cultured rat central nervous system--an autoradiographic study

The cellular localization of the binding of radioactive noradrenaline and alpha- and beta-adrenoceptor antagonists was studied in organotypic cultures of rat cerebellum, brain stem and spinal cord using autoradiography. In cerebellar cultures, many neurones, which appeared to be Purkinje cells, were labelled by [3H]noradrenaline and by the beta-antagonists [3H]dihydroalprenolol and [3H]carazolol, whereas no binding of the alpha-antagonists [3H]prazosin and [3H]rauwolscine was detected. In cultures of spinal cord and brain stem, [3H]noradrenaline and the beta-antagonists were bound to many large neurones. Binding of [3H] alpha-antagonists was observed to a small number of brain stem and spinal neurones, the labelling being much weaker than that produced by the [3H] beta-antagonists. The antidepressant [3H]desmethylimipramine was bound to many neurones and glial cells in cerebellar, brain stem and spinal cord cultures. Glial cells also possessed binding sites for [3H]noradrenaline and alpha- and beta-adrenoceptor antagonists, findings that are consistent with recent electrophysiological observations which indicate the existence of alpha- and beta-adrenoceptors on cultured astrocytes.

Organotypic monolayer cultures of nervous tissue

Cultivation of nervous tissue by means of the roller-tube technique yields thin organotypic cultures. Explants or slices prepared from 1- to 20-day-old rats are embedded in a plasma clot on flying coverslips and cultivated for weeks in roller-tubes. Due to the flattening of the tissue, individual nerve cells are often arranged in monolayer thickness and can, therefore, be viewed with phase-contrast microscopy. This technique is utilized to culture and co-culture nervous tissue derived from various brain regions. The degree of organotypic organization depends on the age of the animals used for culturing. Stable intracellular recordings arae obtained from nerve cells which are impaled under visual control. In view of the accessibility of individual living cells, this approach seems to be particularly well-suited for physiological and pharmacological studies on morphologically identified nerve cells.

Efflux of potassium from neurones excited by glutamate and aspartate causes a depolarization of cultured glial cells

The time course of the depolarization of cultured astrocytes and neurones by glutamate and aspartate corresponds well with the increase of the extracellular K+ concentration ([K +]0) measured with an ion-sensitive microelectrode placed in the close vicinity of the cells tested. It is concluded that the depolarization of glial cells is caused by an efflux of K+ from neighbouring neurones during their excitation by the amino acids.

Action of GABA and glycine on the membrane potential of culture astrocytes and the extracellular concentration

The depolarization of cultured astrocytes by GABA and glycine correlates in amplitude and time course with the increase of the extracellular K+ -concentration during perfusion with these amino acids. It is suggested that the glial depolarization is caused by an efflux of K+ from neighbouring neurones activated by the amino acid transmitters.

Release of acetylcholinesterase by cultured spinal cord cells

The release of acetylcholinesterase from neurons was studied using cultured chick-embryo spinal-cord cells. Cells dissociated from 12-day-old chick-embryo spinal cords were grown in culture for 10-12 days. Numerous well differentiated spinal neurons were found after 7-10 days in culture. Acetylcholinesterase activity per dish increased by 60-fold from days 2-12. Acetylcholinesterase was released into the surrounding media by the cells when they were incubated either in the standard culture medium or the serum-free medium. Acetylcholinesterase release was significantly reduced when protein synthesis and microtubules were disrupted by cycloheximide and colchicine, respectively. Histochemical localization of acetylcholinesterase indicated that the synthesis and relase of acetylcholinesterase are attributable to neurons. Cultured chick-embryo brain and neuroblastoma cells also released acetylcholinesterase into the media. These results are discussed with regard to possible physiological roles for acetylcholinesterase secretion from neurons.

Acetylcholinesterase distribution in chick spinal cord cultures. A light and electron microscope study

Explants of 10--12 day chick embryo spinal cord were cultured by coverslip-roller tube method for 3-80 days. The cellular and subcellular localization of acetylcholinesterase activity in cultured neurons was studied by the thiocholine techniques of Karnovsky and Roots and Lewis and Shute. At the light microscopic level, acetylcholinesterase was demonstrated in the neurons of both ventral and dorsal horn regions. Occasionally neurons migrated in the outgrowth zone exhibited strong intracellular activity. At the electron microscopic level, acetylcholinesterase activity was found in the nuclear envelope, granular endoplasmic reticulum and the Golgi apparatus of the neurons. No enzyme reaction was detected in the glial cell cytoplasm.

Uptake of (3H)glycine and (14C)glutamate by cultures of chick spinal cord

1. Spinal cord explants from chick embryos, grown in culture for up to 16 days, rapidly accumulated [(3)H]glycine and [(14)C]glutamate when incubated at 25 degrees C in a medium containing either 2 x 10(-10)M glycine or 4.8 x 10(-8)M glutamate.2. After 90 min incubation, a tissue/medium ratio of 60:1 and 20:1 was attained for [(14)C]glutamate and [(3)H]glycine respectively.3. The uptake systems, in addition to requiring sodium ions in the medium, were temperature sensitive, showed saturation kinetics, and were inhibited by ouabain.4. For the glutamate and glycine accumulation the K(m) value was 4.3 x 10(-5) and 4.1 x 10(-5)M respectively, indicating that a high affinity uptake process is involved.5. The rate of accumulation of both glutamate and glycine increased in cultures between the ages of 3 and 10 days thus matching their morphological development.6. In light of previous evidence, the demonstration of an active transport mechanism for both glutamate and glycine in spinal-cord-cultures that also shows a relationship with morphological maturity, suggests that these two amino acids may play a major role in spinal cord function.

Choline acetyltransferase activity is increased in combined cultures of spinal cord and muscle cells from mice

The activity of choline acetyltransferase was more than tenfold greater in combined cultures of spinal cord and muscle cells than in cultures of spinal cord cells alone. This increase was associated with the formation of functional neuromuscular junctions in culture. Counts of silver-stained cells and determinations of other enzyme activities indicated that the increased choline acetyltransferase activity was not due to nonspecific neuronal survival but reflected greater activity in the surviving neurons. Hence, muscle had a marked, highly specific trophic effect on the cholinergic neurons that innervated it.

Neurotrophic effect on isolated chick embryo muscle in culture

Acetylcholinesterase activity in cultures of dissociated skeletal muscle prepared from the thigh muscle of the 10-day-old chick embryo was increased by the presence of innervating spinal cord explants, spinal cord explants in a parabiotic environment, and by media containing brain-spinal cord extract.