Kinetics of [3H]acetylcholine synthesis and release in primary cell cultures from mammalian CNS

Recovery of [3H]acetylcholine synthesis after AF64A-treatment in primary, neuron-enriched, rat septal-hippocampal and striatal cultures

Neuron-enriched cultures prepared from several different rat brain regions were incubated with 10 microM or 30 microM monoethylcholine mustard aziridinium ion (AF64A) under conditions (1 h, 37 degrees C in Krebs Ringer buffer) that reduced acetylcholine (ACh) synthesis coupled to high-affinity choline uptake, without affecting choline acetyltransferase activity. Co-cultures of septum-hippocampus and cultures of striatum were similarly sensitive to the AF64A-induced inhibition of ACh synthesis. However, ACh-synthesis recovered more rapidly in the striatal cultures than in septal-hippocampal co-cultures after AF64A washout. In septal-hippocampal co-cultures, neither tunicamycin (20 micrograms/ml) nor cycloheximide (0.5 microgram/ml) had any effect on the basal synthesis of ACh or its recovery within 24 h following 10 microM AF64A washout. However, the recovery of ACh synthesis in these co-cultures after 30 microM AF64A-washout was blocked by either tunicamycin or cyclohexamide. Neither tunicamycin nor cyclohexamide interfered with ACh-synthesis recovery after washout of 30 microM AF64A in striatal cultures. These studies suggest that the turnover of high-affinity choline transporters can be modulated in a brain-region specific manner in intact primary neuronal cultures.

Cholinergic but not GABAergic neuronal markers are decreased in primary neuronal cultures treated with choline mustard

Nitrogen mustard analogues of choline are potent irreversible inhibitors of high-affinity choline transport at the cholinergic presynaptic nerve terminal in vitro. Ethylcholine mustard aziridinium ion, and to a lesser extent choline mustard aziridinium ion, have been used as tools to chemically lesion cholinergic neurons in the central nervous system. The selectivity of these compounds as neurotoxins for cholinergic neurons in vivo has been questioned and the mechanism by which they mediate neuronal death has not been elucidated. The objective of the present study was to investigate the selectivity of choline mustard aziridinium ion on embryonic rat brain neurons maintained in primary culture. The effect of choline mustard aziridinium ion on levels of cholinergic neuronal markers was compared with markers for GABAergic neurons as a measure of neuronal specificity. Choline mustard aziridinium ion at 10 and 30 microM irreversibly inhibited hemicholinium-sensitive, high-affinity choline transport into the cultured neurons without altering sodium-dependent, high-affinity GABA transport. Similarly, incubation of the neurons for 30 min in the presence of 10 microM choline mustard aziridinium ion led to a decrease in choline acetyltransferase activity of the cultures which was maintained for 72 h; glutamic acid decarboxylase activity was not altered under the same experimental conditions. Protein and DNA content and DNA-to-protein ratios of the choline mustard aziridinium ion-treated cultures were monitored as indicators of generalized cellular damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Choline and acetylcholine metabolism in slice cultures of the newborn rat septum

The incorporation of [3H]choline into acetylcholine and other choline-containing compounds was investigated in slice cultures of the septal area of newborn rats. At choline concentrations in the range of the high affinity transport mechanism (0.1-1 microM) most of the labeled choline was incorporated into phosphorylcholine, followed by lipids, acetylcholine and the free choline pool. Hemicholinium-3 (1-10 microM) lead to a marked decrease of acetylcholine synthesis, whereas choline accumulation or phosphorylcholine synthesis were not decreased. Both basal and K+-induced release of acetylcholine were Ca2+ dependent. The efflux of choline was not stimulated by high K+. When choline was absent from the incubation medium, the slices were able to liberate significant amounts of the [3H]choline previously incorporated into phospholipids, and were also able to synthesize some acetylcholine. In choline-free medium, acetylcholine synthesis was greatly enhanced by depolarization. During the period in culture, there was a decrease of the incorporation rate of [3H]choline into phosphorylcholine and an increase of the incorporation rate into acetylcholine. The tissue structure was well preserved after several weeks in culture. After staining for acetylcholinesterase, the cholinergic neurons in the cultures showed a similar morphology to that seen in situ. The main conclusions of the present study are: cholinergic neurons in slice cultures develop and behave in a manner which is very similar to their in situ counterparts; the main divergence from previous studies of choline metabolism in tissue culture is the substantial incorporation rate of choline into acetylcholine at choline concentrations in the range of the high affinity uptake mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological and electrophysiological aspects of dissociated cultures of rat CNS

Rat central nervous system has been cultured up to 6 weeks after complete dissociation. Maturation of different cell types has been followed in the quasi monolayer by phase contrast microscopy. Dorsal root ganglion (DRG) neurones usually differed from central nervous system (CNS) neurones by their spherical shape accompanied by only one or two processes, exact identification of cell types, however, was usually only possible by combining morphology with electrophysiology. Scanning electron-microscopy revealed a more extensive arborization of neurites and a higher number of presumed synaptic structures in cultures after 2 weeks of culturing. Layers of ependymal cells were also found. The different cell types were further identified by determining their membrane properties. Glial cells had higher resting membrane potentials (-56 +/- 9.7 mV) than CNS neurones (-49 +/- 10.2 mV), while the membrane potential of DRG neurones lay in-between the two (-53 +/- 1.7 mV). The sequence for input resistance was: DRG neurones (30 +/- 9.3 M omega) greater than CNS neurones (18 +/- 10.5 M omega) greater than glial cells (9.3 +/- 5.2 M omega). In CNS neurones the input resistance is correlated with the membrane potential, which is not the case for glial cells. Action potentials of DRG neurones exhibited delayed repolarisation increasing the spike duration to three times that of CNS neurones.

Nervous system-specific protein D2 associated with neurite outgrowth in nerve cell cultures

Dissociated cerebral cells from fetal rat brain were grown in culture for various periods. After 12 days in culture the nervous system-specific surface membrane protein D2 reached both maximal specific concentration and maximal amount. Moreover, most of this D2 protein was in the perinatal form with high electrophoretic mobility. The amount of perinatal D2 protein possibly followed the amount of neurites in this system. D2 protein was also found in 2 neuroblastoma C-1300 clones: Neuro 2a and NB 41A3. By addition of gangliosides, Neuro 2a cells could be induced to differentiate and form processes, and D2 protein was significantly increased. However, in both differentiated and undifferentiated neuroblastoma cells D2 protein was present in the adult form with slow electrophoretic mobility. NB 41A3 cells were unaffected by gangliosides and D2 protein was not changed. Thus ganglioside treatment of Neuro 2a tumor cells was followed by a cellular response only partly similar to developmental events concomitant to differentiation of primary cells.

Tetanus toxin and botulinum A toxin inhibit acetylcholine release from but not calcium uptake into brain tissue

Slices or particles from rat forebrain cortex were preloaded with [3H]choline, and the release of [3H]acetylcholine was evoked with potassium ions in a superfusion system. Release depended on the presence of calcium. 1. Incubation of the preloaded tissue preparation for 2 h with tetanus or botulinum A toxin did not change the [3H]acetylcholine content or the ratio [3H]acetylcholine/[3H]choline. Tetanus toxin diminished, dependent on dose and time, the release of [3H]acetylcholine evoked by 25 mM K+. It was about ten times more potent than botulinum A toxin. The effect of botulinum toxin was due to its neurotoxin content. Raising the potassium concentration partially overcame the inhibition by the toxins. Hemicholinium-3, applied to preloaded slices, left the subsequent [3H]acetylcholine release unchanged. Pretreatment of particles with neuraminidase diminished the content of long-chain gangliosides to the detection limit. Such particles remained fully sensitive to tetanus toxin, and at least partially sensitive to botulinum A toxin. 2. The potassium or sea anemone toxin II stimulated uptake of 45Ca2+ into cortex synaptosomes or particles was not inhibited by either toxin. Both toxins appear to impede the Ca2+-dependent mobilization of an easily releasable acetylcholine pool, without inhibiting the transmembranal calcium fluxes.

Replication of Borna disease virus in cell cultures

Borna disease (BD) virus from infected brain tissue of horses or rabbits could be grown in embryonic brain cells from rabbits or rats with high virus yields. The cells became persistently infected and could be subcultivated without loss of infectivity. Cocultivation of infected rabbit brain (ERB) cells with GMK-, Vero-, or MDCK-cells led to persistently infected cell lines. BD virus grown in MDCK cells after cocultivation became adapted to this cell type and could be used directly for further infection of MDCK cells.

Rat nerve cell cultures in pharmacology and toxicology

A tissue culture system of the rat embryonic central nervous system is described which allows morphological, biochemical, and electrophysiological approaches. Examples for each of the mentioned methods are given. Developmental features of these cultures are described as they appear in the phase contrast microscope over a period of 4 weeks. Further details are shown by a scanning electron microscopic photograph. Tetanus toxin induced changes in acetylcholine synthesis and release serve to demonstrate the usefulness of the model system for biochemical approaches. Intracellular recordings of neurons reveal synaptic potentials as well as spontaneously fired action potentials. Thus an ample use of rat central nervous system cultures in pharmacology and toxicology should provide completely new insights into the action of drugs and toxins at the cellular and molecular level.

Suppression of 3H-acetylcholine release from primary nerve cell cultures by tetanus and botulinum-A toxin

Primary nerve cell cultures derived from embryonic rat central nervous system form [3H]ACh from exogenous [3H]Ch, and release it upon potassium depolarization. Pretreatment of the cultures with botulinum-A toxin or tetanus toxin diminishes the cellular accumulation of [3H]ACh. Poisoning the cultures during the period of [3H]Ch uptake fails to lower [H]ACh formation. Dependent on dosage, both toxins suppress the release of [3H]ACh upon potassium depolarization. Heat-denaturated toxins as well as tetanus toxin preincubated with tetanus antitoxin were without effect.