Butanol extracts from myelin fragments. III. SDS-urea gel electrophoretic studies

Summary The butanol extracts from myelin fragments showing 5-HT binding capacity were studied by SDS-urea gel electrophoresis. 5 main bands were observed and their molecular weights were determined by the method of Ferguson relationship, and revealed that these extracts contained proteolipid protein, DM-20 and basic proteins. Furthermore, the reconstituted fraction with crude basic proteins and lipids showed the saturable binding capacity for C¹⁴·5-HT.Acknowledgment. We thank Prof. T. Iwamoto for his encouragement during the course of this study.     

5-Hydroxytryptamine binding to butanol extracts from myelin fragments

Summary The myelin fraction of rat brain stem was treated with butanol-water mixtures, and the extracted proteolipids were separated by Sephadex LH₂₀ column chromatography. 2 peaks of proteolipids eluted in chloroform-methanol 4/1 showed the binding capacity for C¹⁴·5-HT. This finding suggests the necessity of the more careful investigations for the probability of proteolipids as receptor proteins in the central nervous system.     

Cardioactive peptides of the CNS of the pulmonate snailLymnaea stagnalis

Summary In the pulmonate snailLymnaea stagnalis the cardioactive effects (tested on isolated auricles) of acetylcholine (ACh), 5-hydroxytryptamine (5-HT), the bivalve tetrapeptide FMRFamide, and of chromatographically separated snail brain substances have been established. Besides ACh and 5-HT, in brain extracts, small FMRFamide-like and large cardioexcitatory peptides were found.     

The enteric neural receptor for 5-hydroxytryptamine

Summary An enteric neural receptor for serotonin (5-HT) has been characterized. This receptor was assayed, using³H-5-HT as a radiologand, by rapid filtration of isolated enteric membranes and by radioautography. In addition, intracellular recordings were made from ganglion cells of the myenteric plexus. High affinity, saturable, reversible, and specific binding of³H-5-HT was demonstrated both to membranes of the dissected longitudinal muscle with adherent myenteric plexus and the mucosa-submucosa. Radioautographs showed these³H-5-HT binding sites to be in myenteric ganglia and in a broad unresolved band at the mucosal-submucosal interface. Antagonists active at receptors for other neurotransmitters than 5-HT, at either of the two known types of CNS 5-HT receptor, and at 5-HT uptake sites on serotonergic neurons failed to inhibit binding of³H-5-HT. The structural requirements of analogues for binding to the enteric 5-HT receptor matched the known pharmacology of M or neural 5-HT receptors. A novel 5-HT antagonist was found. This compound, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide (5-HTP-DP), antagonized the action of 5-HT on type II/AH cells of the myenteric plexus but did not affect the release or actions of acetylcholine (nicotinic or muscarinic) or substance P. 5-HTP-DP was also an equally potent displacer of³H-5-HT from its binding sites on enteric membranes. It is concluded that the sites responsible for specific binding of³H-5-HT are enteric M or neural 5-HT receptors. These receptors differ from those now known to be present in the CNS.     

The effect of bovine myelin basic protein on uptake and release of H3-labelled 5-hydroxytryptamine,L-noradrenalin and γ-aminobutyric acid in rat cortex slices

Summary At concentrations above 10^–5 M myelin basic protein (MBP) induced a small inhibition of the uptake of H³-5HT and H³-NA into rat cortex slices. Release of 5HT, NA and Gaba was not affected by 10^–5 M MBP.Acknowledgment. The authors wish to thank W. Bucher for the preparation of MBP.     

The occurrence of 5-hydroxytryptamine in the holothurian,Pentacter crassa

Summary 5-Hydroxytryptamine (5-HT) and hypoxanthine were isolated chromatographically from the holothurianPentacter crassa. This study was initiated as a result of the observed hypotensive activity of aP. crassa extract. This activity was also encountered in extracts of the holothuriansThelenota ananus andStichopus chloronatus and can be attributed to 5-HT.     

Some factors affecting Malpighian tubule fluid secretion and transepithelial potential inLocusta migratoria L.

Summary Both fluid secretion and transepithelial potential were stimulated by cAMP. Fluid secretion was unaffected by 5-HT over the concentration range 10^–8–10^–4 M. The presence of ouabain in the bathing medium effected a decrease in transepithelial potential.     

Butanol extracts from myelin fragments: Morphological and biochemical aspects of the re-formed membranes prepared from myelin butanol extracts

Summary The re-formed membranes prepared from butanol extracts of myelin were examined by morphological and biochemical methods. Using freeze-fracturing, re-formed membranes showed 2 types of assembly of membrane particles, i.e., myelin-like and cluster arrangements. Moreover, SDS-urea disc gel electrophoresis indicated that the protein composition of these membranes reflected that of the myelin fragments.Acknowledgment. This work was supported by a research grant (No. 467 384) from the Ministry of Education, Japan.     

Effect of large mesencephalic-diencephalic lesions on the noradrenalin,dopamine and 5-hydroxytryptamine neurons of the central nervous system

Zusammenfassung Nach Ausführung von grossen symmetrischen mesencephalisch-dicncephalischen Läsionen in Ratten konnte mit Hilfe von biochemischen und histochemischen Methoden eindeutig festgestellt werden, dass die Dopamin (DA), Noradrenalin (NA) und 5-Hydroxytryptamin (5-HT) enthaltenden Nerventerminalen im Prosencephalon zu grossen aufsteigenden DA, NA und 5-HT Neuronsystemen gehören. Die Zellkörper dieser Neuronensysteme sind im Gehirnstamm lokalisiert. Dies deutet darauf hin, dass ein einzelnes NA Neuron Gebiete innervieren kann, die weit auseinander liegen, zum Beispiel auf der einen Seite im Cerebellum, auf der anderen im Prosencephalon.     

Inhibition and sex specific induction of spawning by serotonergic ligands in the zebra musselDreissena polymorpha (Pallas)

Serotonin (5-hydroxytryptamine, 5-HT) stimulates spawning in the zebra mussel (Dressena polymorpha), a macrofouling European bivalve that has recently invaded North America. To develop methods of controlling zebra mussel spawning, two vertebrate serotonin antagonists, methiothepin and metergoline, known to bind with high affinity to snail 5-HT receptors, were tested for their ability to block 5-HT-induced spawning in zebra mussels. Methiothepin inhibited 5-HT-induced spawning at concentrations as low as 10^–6 M. Metergoline (10^–4 M) inhibited 5-HT-induced spawning; however, at lower concentrations (10^–8 to 10^–5 M), metergoline by itself significantly induced spawning in male, but not female zebra mussels. Metergoline (10^–5 M)-induced male spawning was inhibited by 10^–5 M methiothepin. Thus, methiothepin is the most effective inhibitor and metergoline the most powerful inducer of spawning yet tested in zebra mussels.     

The influence of ambient temperature on thermoregulatory responses to intraventricularly injected monoamines in sheep,goats and rabbits

Zusammenfassung Zur Erklärung der Effekte auf die Thermoregulation in Schafen, Ziegen und Kaninchen bei verschiedenen Umwelttemperaturen von intraventrikulären Injektionen von Noradrenalin (NA) und 5-Hydroxytryptamin (5-HT) wurde ein einfaches Neuronenmodell vorgeschlagen. Diese Monoamine entfalten nicht in allen Situationen eine reziproke Wirkung. 5-HT führt zu einem Anstieg des Wärmeverlustes und einer Hemmung der Wärmebildung. NA hemmt sowohl Wärmeverlust wie auch Wärmebildung 19.     

Effect of des-Tyr1-γ-endorphin on serotonin metabolism in rat brain regions

Summary Intracerebroventicular (i.c.v.) administration of des-Tyr¹-γ-endorphin (0.1 and 1.0 μg) caused a decrease of the serotonin (5-HT) concentration of the hippocampus. The concentration of 5-HIAA and the pargyline-induced alterations in 5-HT and 5-HIAA were not affected. No effects were noticed in other brain regions. Acknowledgement. The skilful technical assistance of Ms Henny de Vos Burchart-Lodewijks and Mrs H.A. Spierenburg and J.A. Meijer is gratefully acknowledged. Des-Tyr¹-γ-endorphin was a gift of Dr. H.M. Greven, Organon International B.V., Oss, The Netherlands. To whom reprint requests should be addressed.     

Über den Einfluss von Desoxycorticosteron auf Kontraktur und Kaliumfreisetzung durch Acetylcholin an der innervierten und denervierten Skelettmuskulatur

Summary The release of potassium ions from striated muscle, and the changes in mechanical tension developed by the gastrocnemius muscle on intraarterial injection of ACh, were investigated by isolated perfusion of the hind limbs in cats. The reaction of the normal innervated and chronically denervated muscle in the same animal were compared before and during perfusion with 2·10^–4 M/l desoxycorticosterone glucoside (DCG). The following results were obtained: after perfusion with DCG no change in the spontaneous release of potassium ions occurred neither on the innervated nor on the denervated muscle. The potassium release following intra-arterial injections of various doses of ACh was significantly reduced on innervated and denervated muscle. On the denervated muscle there was also a considerable reduction of the height of contractures caused by ACh administration. The results make it probable that DCG acts by an inhibition of depolarisation in the same way asd-tubocurarine.     

The role of sialic acid in 5-HT binding to synaptic membranes

Summary The high affinity binding of [¹⁴C]5-HT to nerve ending membranes isolated from rat brain is not affected by neuraminidase treatment. The specificity of ligand receptor interaction was demonstrated by displacement studies with tryptamine derivatives, noradrenaline, and acetylcholine.The expert technical assistance of Miss Christiane von Winterfeld is appreciated. This work was supported by a grant of the Deutsche Forschungsgemeinschaft.     

Sérotonine et scglycémie chez les crustacés

Summary Injection of 0.2 cm³ of 5-HT 0.1% inCarcinus maenas has a powerful hyperglycaemic effect and determines at the same time a dispersion of the melanin granules in chromatophores of eyestalkless crabs. In both instances, 5-HT mimics the effects of the injection of an extract from the eyestalks.     

Inhibition of insect nerve cord phosphorylase activity by 5-hydroxytryptamine

Zusammenfassung Die Phosphorylaseaktivität der in vitro mit 1×10^–4 M 5-Hydroxytryptamine inkubierten Insektennervenstränge war bedeutsam verringert. Der Effekt schien konzentrationsabhängig zu sein, da er sich mit steigender 5-HT-Konzentration verstärkte. 5-HT verminderte die aktive Form des Enzyms im Verhältnis zu dessen inaktiver Form. Epinephrin hatte keine Wirkung.     

Myelin basic protein: a multifunctional protein

Myelin basic protein (MBP), the second most abundant protein in central nervous system myelin, is responsible for adhesion of the cytosolic surfaces of multilayered compact myelin. A member of the ‘intrinsically disordered’ or conformationally adaptable protein family, it also appears to have several other functions. It can interact with a number of polyanionic proteins including actin, tubulin, Ca²⁺-calmodulin, and clathrin, and negatively charged lipids, and acquires structure on binding to them. It may act as a membrane actin-binding protein, which might allow it to participate in transmission of extracellular signals to the cytoskeleton in oligodendrocytes and tight junctions in myelin. Some size isoforms of MBP are transported into the nucleus and thus they may also bind polynucleotides. Extracellular signals received by myelin or cultured oligodendrocytes cause changes in phosphorylation of MBP, suggesting that MBP is also involved in signaling. Further study of this very abundant protein will reveal how it is utilized by the oligodendrocyte and myelin for different purposes. Received 2 March 2006; received after revision 12 April 2006; accepted 16 May 2006     

Sodium concentration and the effect of angiotensin II on iieal smooth muscle

Zusammenfassung Die kontraktile Reaktion des isolierten Meerschweinchen-Ileums auf Angiotensin II variierte direkt mit der Natriumkonzentration der Nährflüssigkeit, nicht aber bei ACh; Atropin (10^–6 g/ml) reduzierte die Wirkung auf Angiotensin um 60–70% und hob die Wirkung auf äquivalente Mengen von ACh auf. In atropinhaltiger Ringerlösung potenzierte ein hoher Natriumgehalt (+ 30 meq./l) die Reaktion auf Angiotensin zehnfach.     

5-HT hyperpolarization of bullforg sympathetic ganglion cell membrane

Zusammenfassung Die Membran der sympathischen Ganglienzelle des Ochsenfrosches (Rana catesbiana) wird durch 5-HT depolarisiert; 5-HT erzeugt jedoch in Gegenwart von Nicotin eine Hyperpolarisation. Es scheint, dass sowohl die Depolarisation als auch die Hyperpolarisation von 5-HT durch direkte Wirkung auf die Zell-Membran zustande kommt. Die durch 5-HT erzeugte Hyperpolarisation zeigte ähnliche Eigenschaften wie des «slow IPSP» welches jedoch während der Entwicklung der 5-HT Hyperpolarisation stark zunimmt. Es wird vermutet, dass 5-HT wahrscheinlich nicht als Überträgerstoff für das «slow IPSP» in Frage kommt.     

Platelets as a model for neurones?

The multiple biochemical and pharmacological similarities existing between blood platelets and 5-hydroxytryptamine (5-HT)-containing neurones of the CNS point to the platelets as a reliable model for the biochemical characterization of 5-HT releasers and uptake blockers which interfere with the storage and the active carrier mechanism of 5-HT in the neurones, respectively. In addition, the affinity displayed by dopamine and by dopaminergic neurotoxin MPP⁺ for the platelet 5-HT transport and storage indicates also some similarities between platelets and the dopaminergic system of the CNS. Since human platelets contain almost exclusively monoamine oxidase type B (MAO-B), they can be used as a source for the purification and characterization of this human enzyme. Human platelets thus offer an excellent peripheral model to indirectly assess the degree and duration of MAO-B inhibition occurring in the CNS. To date, knowledge of the many biochemical mechanisms underlying platelet physiology is still fragmentary. In fact, the functional role of binding sites located on the platelet cytoplasmic membrane, i.e. their coupling to a specific transmembrane signalling mechanism, is still in need of a precise biochemical and physiological characterization.