Type I like behavior of the type II alpha 7 nicotinic acetylcholine receptor positive allosteric modulator A-867744

Cognitive impairment often involves the decreased expression or hypofunction of alpha 7-type nicotinic acetylcholine receptors (alpha 7 nAChRs). Agonists or positive allosteric modulators (PAMs) of alpha 7 nAChRs are known to be potential treatments for dementias, different neurodegenerative disorders, pain syndromes and conditions involving inflammation. In some of these conditions, it is desirable to maintain the temporal precision of fast cholinergic events, while in others, this temporal precision is unnecessary. For this reason, the optimal therapeutic effect for distinct indications may require PAMs with different mechanisms of action. The two major mechanisms are called "type I", which are compounds that augment alpha 7 nAChR-mediated currents but maintain their characteristic fast kinetics; and "type II", which are compounds that produce augmented and prolonged currents. In this study, we performed a kinetic analysis of two type II PAMs of the alpha 7 nAChR: PNU-120596 and A-867744, using a fast perfusion method that allowed high temporal resolution. We characterized the type of modulation produced by the two compounds, the state-dependence of the modulatory action, and the interaction between the two compounds. We found fundamental differences between the modulation mechanisms by PNU-120596 and A-867744. Most importantly, during brief agonist pulses, A-867744 caused a strikingly type I-like modulation, while PNU-120596 caused a type II-like prolonged activation. Our results demonstrate that specific compounds, even though all labeled as type II PAMs, can behave in completely different ways, including their onset and offset kinetics, state preference, and single channel open time. Our results emphasize that subtle details of the mechanism of action may be significant in assessing the therapeutic applicability of alpha 7 nAChR PAM compounds

A depresszió neurokémiai hátterének vizsgálata = Study of the neurochemical background of depression

Kutatási projektünk elsődleges célja az volt, hogy megpróbáljuk felderíteni a depresszió hatterében álló neurokémiai történéseket. Munkánk során megállapítottuk, hogy a jelenleg használt antidepresszánsok a monoamin szintek befolyásolásán kívül egyéb mechanizmusokkal (a nikotinikus acetilkolin receptorok és az NMDA receptorok, valamint a feszültségfüggő Na+-csatornák gátlásán kesresztül) is módosíthatják a központi idegrendszer működését, mely hatások hozzájárulhatnak az antidepresszáns hatás kifejlődéséhez. Kidolgoztuk az antidepresszánsok egy új osztályának, az aktív antidepresszánsoknak az elméleti alapjait, valamint leírtuk a monoamin transzporterek egy érdekes tulajdonságát, a szerotonin transzporterek heterológ noradrenalin felvételi képességét. Ez a felismerésünk rávilágít az átfedő monoaminerg rendszerek közötti szoros együttműködésre és elősegítheti az szelektív szerotonin reuptake inhibítor vegyületek hatásmechanizmusának jobb megértését. Eredményeink felhasználásával közelebb kerülhetünk a depresszió kialakulához vezető folyamatok tisztázásához, és a potenciális új központi idegrendszeri célpontok azonosítása elősegítheti az eredményesebb kezelési módok kialakítását. | The major aim of our research project was the investigation of the neurochemical background of depression. We found that the currently used antidepressant drugs, beyond the regulation of the monoaminergic neurotransmission, are able to influence the function of the central nervous system through other mechanisms like the inhibition of nicotinic acetylchoine receptors, NMDA receptors and voltage sensitive Na+-channels. These interactions might contribute to the development of the antidepressant effect. We have elaborated the theoretical basis of a new class of antidepressant compounds, the so-called active antidepressants and have described an interesting new feature of the monoamine transporters, the heterologous NA reuptake through the serotonin transporters. This finding sheds light on the close interaction of overlapping monoaminergic systems and might help the better understanding of the mechanism of action of selective serotonin reuptake inhibitors. Our results might help to elucidate the neurochemical background of depression and the identification of novel targets in the central nervous system might lead to the development of novel therapeutic strategies

Nemszinaptikus transmisszió: egy új megközelítés az alapvető agy funkciók megértéséhez = Nonsynaptic transmission: a new pathway to understand major brain functions

A két-foton mikroszkópia használata új információkat szolgáltatott a nemszinaptikus kölcsönhatásokról szubmikronos anatómiai struktúrákban. Feltérképeztük a technika felhasználásának lehetőségeit a különböző szövetpreparátumok, idegsejttípusok esetében. A membrán Na+/Ca2+ cserélő gátlása elsősorban a dendrittörzsben befolyásolja a szinaptikus Ca2+ tranzienseket, és szabályozza a tüske-dendrit kapcsolatot. A dendritikus Ca2+ válaszok szintjén a noradrenalin pozitív hatású a dendritikus integráció kapacitásaira nézve, elősegíti a dendritikus potenciálok keletkezését, előnyös a munkamemóriára nézve. Kísérleteink feltárták a nikotin sokrétű serkentő hatásait a dendritek funkcióira nézve, így az akciós potenciálok terjedésének erősítését, spontán válaszok kialakulását a piramissejtek tüskéiben, illetve az interneuronok dendrittörzsében. A farmakológiai alkalmazások közül az antidepresszánsok hatásait vizsgáltuk. Elképzelhető, hogy az antidepresszánsok a lassú inaktivált állapot stabilizálásának keresztül gátolják a Na+ csatorna funkciót úgy, hogy segítsék a depressziós neurális "körök" oldódását. A terápia során kialakuló koncentráció viszonyokban a fluoxetin és a dezipramin az NMDA receptorok működését hatékonyan gátolhatják, ami fontos eleme lehet a depresszió oldásának. | The use of two-photon microscopy yielded novel information about the nonsynaptic interactions in submicron anatomical structures. We mapped the applicational possibilities of this technique using various tissue preparations and neuron types. The inhibition of the membrane Na+/Ca2+ exchanger primarily influenced the synaptic Ca2+ transients in the dendrite shaft and regulate locally the dendrite/spine connectivity. At the level of the dendritic Ca2+ responses, noradrenaline has a positive effect on the capacity of dendritic integration, promotes the initiation of dendritic spikes, and enhances working memory. Our experiments revealed that nicotine has multiple effects on dendritic functions including the strengthening the propagation of action potentials in the dendrite and inducing spontaneous responses in dendritic spines of the pyramidal neurons and dendrites of interneurons. Among the pharmacological applications, we studied the effects of antidepressants. It is possible that the antidepressants block the function of the Na+ channel through the stabilization of the inactivated state in a way that helps unbound the depressive "circuits". At therapeutically relevant concentrations fluoxetine and desipramine can efficiently inhibit the function of the NMDA receptor that might be an important element of antidepressive mechanisms

Treatment of relapsing multiple sclerosis in Hungary – consensus recommendation from the Hungarian neuroimmunology society

Multiple sclerosis (MS) may impact quality of life, careers and family plans of the affected individuals. The current treatments with disease modifying therapies aim to prevent people with MS (pwMS) from disability accumulation and progression. Different countries have different reimbursement policies resulting in inequalities in patient care among geographical regions. Access to anti-CD20 therapies for relapsing MS is restricted in Hungary because therapy of individual cases only is reimbursed. In the light of the latest research and national guidelines, 17 Hungarian MS experts agreed on 8 recommendations regarding relapsing pwMS using the Delphi round method. Strong agreement (> 80%) was achieved in all except one recommendation after three rounds, which generated a fourth Delphi round. The experts agreed on treatment initiation, switch, follow-up and discontinuation, as well as on special issues such as pregnancy, lactation, elderly population, and vaccination. Well-defined national consensus protocols may facilitate dialogue between policymakers and healthcare professionals and thus contribute to better patient care in the long run

Non-blocking modulation contributes to sodium channel inhibition by a covalently attached photoreactive riluzole analog

Sodium channel inhibitor drugs decrease pathological hyperactivity in various diseases including pain syndromes, myotonia, arrhythmias, nerve injuries and epilepsies. Inhibiting pathological but not physiological activity, however, is a major challenge in drug development. Sodium channel inhibitors exert their effects by a dual action: they obstruct ion flow ("block"), and they alter the energetics of channel opening and closing ("modulation"). Ideal drugs would be modulators without blocking effect, because modulation is inherently activity-dependent, therefore selective for pathological hyperactivity. Can block and modulation be separated? It has been difficult to tell, because the effect of modulation is obscured by conformation-dependent association/dissociation of the drug. To eliminate dynamic association/dissociation, we used a photoreactive riluzole analog which could be covalently bound to the channel; and found, unexpectedly, that drug-bound channels could still conduct ions, although with modulated gating. The finding that non-blocking modulation is possible, may open a novel avenue for drug development because non-blocking modulators could be more specific in treating hyperactivity-linked diseases