Determining the neurotransmitter concentration profile at active synapses

Establishing the temporal and concentration profiles of neurotransmitters during synaptic release is an essential step towards understanding the basic properties of inter-neuronal communication in the central nervous system. A variety of ingenious attempts has been made to gain insights into this process, but the general inaccessibility of central synapses, intrinsic limitations of the techniques used, and natural variety of different synaptic environments have hindered a comprehensive description of this fundamental phenomenon. Here, we describe a number of experimental and theoretical findings that has been instrumental for advancing our knowledge of various features of neurotransmitter release, as well as newly developed tools that could overcome some limits of traditional pharmacological approaches and bring new impetus to the description of the complex mechanisms of synaptic transmission

Towards the clinical implementation of pharmacogenetics in bipolar disorder.

BackgroundBipolar disorder (BD) is a psychiatric illness defined by pathological alterations between the mood states of mania and depression, causing disability, imposing healthcare costs and elevating the risk of suicide. Although effective treatments for BD exist, variability in outcomes leads to a large number of treatment failures, typically followed by a trial and error process of medication switches that can take years. Pharmacogenetic testing (PGT), by tailoring drug choice to an individual, may personalize and expedite treatment so as to identify more rapidly medications well suited to individual BD patients.DiscussionA number of associations have been made in BD between medication response phenotypes and specific genetic markers. However, to date clinical adoption of PGT has been limited, often citing questions that must be answered before it can be widely utilized. These include: What are the requirements of supporting evidence? How large is a clinically relevant effect? What degree of specificity and sensitivity are required? Does a given marker influence decision making and have clinical utility? In many cases, the answers to these questions remain unknown, and ultimately, the question of whether PGT is valid and useful must be determined empirically. Towards this aim, we have reviewed the literature and selected drug-genotype associations with the strongest evidence for utility in BD.SummaryBased upon these findings, we propose a preliminary panel for use in PGT, and a method by which the results of a PGT panel can be integrated for clinical interpretation. Finally, we argue that based on the sufficiency of accumulated evidence, PGT implementation studies are now warranted. We propose and discuss the design for a randomized clinical trial to test the use of PGT in the treatment of BD

Specificity and Actions of an Arylaspartate Inhibitor of Glutamate Transport at the Schaffer Collateral-CA1 Pyramidal Cell Synapse

In this study we characterized the pharmacological selectivity and physiological actions of a new arylaspartate glutamate transporter blocker, L-threo-ß-benzylaspartate (L-TBA). At concentrations up to 100 µM, L-TBA did not act as an AMPA receptor (AMPAR) or NMDA receptor (NMDAR) agonist or antagonist when applied to outside-out patches from mouse hippocampal CA1 pyramidal neurons. L-TBA had no effect on the amplitude of field excitatory postsynaptic potentials (fEPSPs) recorded at the Schaffer collateral-CA1 pyramidal cell synapse. Excitatory postsynaptic currents (EPSCs) in CA1 pyramidal neurons were unaffected by L-TBA in the presence of physiological extracellular Mg2+ concentrations, but in Mg2+-free solution, EPSCs were significantly prolonged as a consequence of increased NMDAR activity. Although L-TBA exhibited approximately four-fold selectivity for neuronal EAAT3 over glial EAAT1/EAAT2 transporter subtypes expressed in Xenopus oocytes, the L-TBA concentration-dependence of the EPSC charge transfer increase in the absence of Mg2+ was the same in hippocampal slices from EAAT3 +/+ and EAAT3 −/− mice, suggesting that TBA effects were primarily due to block of glial transporters. Consistent with this, L-TBA blocked synaptically evoked transporter currents in CA1 astrocytes with a potency in accord with its block of heterologously expressed glial transporters. Extracellular recording in the presence of physiological Mg2+ revealed that L-TBA prolonged fEPSPs in a frequency-dependent manner by selectively increasing the NMDAR-mediated component of the fEPSP during short bursts of activity. The data indicate that glial glutamate transporters play a dominant role in limiting extrasynaptic transmitter diffusion and binding to NMDARs. Furthermore, NMDAR signaling is primarily limited by voltage-dependent Mg2+ block during low-frequency activity, while the relative contribution of transport increases during short bursts of higher frequency signaling

Fast Homeostatic Plasticity of Inhibition via Activity-Dependent Vesicular Filling

Synaptic activity in the central nervous system undergoes rapid state-dependent changes, requiring constant adaptation of the homeostasis between excitation and inhibition. The underlying mechanisms are, however, largely unclear. Chronic changes in network activity result in enhanced production of the inhibitory transmitter GABA, indicating that presynaptic GABA content is a variable parameter for homeostatic plasticity. Here we tested whether such changes in inhibitory transmitter content do also occur at the fast time scale required to ensure inhibition-excitation-homeostasis in dynamic cortical networks. We found that intense stimulation of afferent fibers in the CA1 region of mouse hippocampal slices yielded a rapid and lasting increase in quantal size of miniature inhibitory postsynaptic currents. This potentiation was mediated by the uptake of GABA and glutamate into presynaptic endings of inhibitory interneurons (the latter serving as precursor for the synthesis of GABA). Thus, enhanced release of inhibitory and excitatory transmitters from active networks leads to enhanced presynaptic GABA content. Thereby, inhibitory efficacy follows local neuronal activity, constituting a negative feedback loop and providing a mechanism for rapid homeostatic scaling in cortical circuits

EpiNet as a way of involving more physicians and patients in epilepsy research: Validation study and accreditation process

open185siObjective: EpiNet was established to encourage epilepsy research. EpiNet is used for multicenter cohort studies and investigator-led trials. Physicians must be accredited to recruit patients into trials. Here, we describe the accreditation process for the EpiNet-First trials. Methods: Physicians with an interest in epilepsy were invited to assess 30 case scenarios to determine the following: whether patients have epilepsy; the nature of the seizures (generalized, focal); and the etiology. Information was presented in two steps for 23 cases. The EpiNet steering committee determined that 21 cases had epilepsy. The steering committee determined by consensus which responses were acceptable for each case. We chose a subset of 18 cases to accredit investigators for the EpiNet-First trials. We initially focused on 12 cases; to be accredited, investigators could not diagnose epilepsy in any case that the steering committee determined did not have epilepsy. If investigators were not accredited after assessing 12 cases, 6 further cases were considered. When assessing the 18 cases, investigators could be accredited if they diagnosed one of six nonepilepsy patients as having possible epilepsy but could make no other false-positive errors and could make only one error regarding seizure classification. Results: Between December 2013 and December 2014, 189 physicians assessed the 30 cases. Agreement with the steering committee regarding the diagnosis at step 1 ranged from 47% to 100%, and improved when information regarding tests was provided at step 2. One hundred five of the 189 physicians (55%) were accredited for the EpiNet-First trials. The kappa value for diagnosis of epilepsy across all 30 cases for accredited physicians was 0.70. Significance: We have established criteria for accrediting physicians using EpiNet. New investigators can be accredited by assessing 18 case scenarios. We encourage physicians with an interest in epilepsy to become EpiNet-accredited and to participate in these investigator-led clinical trials.openBergin P.S.; Beghi E.; Sadleir L.G.; Brockington A.; Tripathi M.; Richardson M.P.; Bianchi E.; Srivastava K.; Jayabal J.; Legros B.; Ossemann M.; McGrath N.; Verrotti A.; Tan H.J.; Beretta S.; Frith R.; Iniesta I.; Whitham E.; Wanigasinghe J.; Ezeala-Adikaibe B.; Striano P.; Rosemergy I.; Walker E.B.; Alkhidze M.; Rodriguez-Leyva I.; Ramirez Gonzalez J.A.; D'Souza W.J.; Calle A.; Palacios C.; Cairns A.; Carney P.; Craig D.; Gill D.; Gupta S.; Lander C.; Laue-Gizzi H.; Hitchens N.; Kiley M.; Lawn N.; Reyneke E.; Riney K.; Tan M.; Tan M.; Thieban M.; Wong C.; van Rijckevorsel G.; Ferrari Strang A.G.; Gifoni A.; Helio L.; Monnerat B.; Brna P.; Donner E.; Jacques S.; Jette N.; McLachlan R.; Mohamed I.; Tran T.P.Y.; Bo X.; Fan S.; Guang Y.; Li M.; Wang K.; Zhang S.; Ladino L.; Christensen J.; Kӧlmel M.S.; Nikanorova M.; Uusitalo A.; Vieira P.; Auvin S.; Ediberidze T.; Gogatishvili N.; Jishkariani T.; Dennig D.; Grimmer A.; Michaelis R.; Schubert-Bast S.; Stephani C.; Stodieck S.; Vollbrandt M.; Zellner A.; Zafeiriou D.; Fogarasi A.; Halasz P.; Chaurasia R.N.; Jain S.; Nair R.; Passi P.; Rajadhyaksha S.; Sattaluri S.J.; Shah H.; Udani V.; Costello D.; Aguglia U.; Bartocci A.; Benna P.; Ferlazzo E.; Laino D.; Spalice A.; Zanchi C.; Ali A.; Lim K.S.; Ramirez A.; Anderson N.; Barber A.; Cariga P.; Cleland J.; Child N.; Davis S.; Dayal V.; Dickson C.; Doran J.; Duncan R.; Giri P.; Herd M.; Hutchinson D.; Jones B.; Kao J.; Kilfoyle D.; Mottershead J.; Muir C.; Nolan M.; Pereira J.; Ranta A.; Sadani S.; Simpson M.; Spooner C.; Timmings P.; Walker E.; Wei D.; Willoughby E.; Wong E.; Wu T.; Olusola T.; Mahmud H.; Mogul Z.; Espinoza J.; Vizarreta J.H.; Baeta E.M.; Teotonio R.; Jocic-Jakubi B.; Lukic S.; Korosec M.; Zgur T.; Eguilaz M.G.; Asztely F.; Sithinamsuwan P.; Anderson J.; Auce P.; Desurkar A.; Hamandi K.; Kelso A.; Sanchez V.; Sidra A.; Smith P.; Wehner T.; Winston G.; Andrade E.; Bensalem-Owen M.; Boudreau M.; Caller T.; Chapman K.; Chari G.; Davis K.; Droker B.; El-Hagrassy M.; Eliashiv D.; Eze C.; Heck C.; Kabir A.; Kolesnik D.; Lam A.; Lopez J.; Maamoon T.; Cohen J.M.; Maganti R.; Nwankwo C.; Park K.; Proteasa S.; Sandok E.; Seinfield S.; Toub J.; Wirrell E.; Arbildi M.; Thien T.T.Bergin, P. S.; Beghi, E.; Sadleir, L. G.; Brockington, A.; Tripathi, M.; Richardson, M. P.; Bianchi, E.; Srivastava, K.; Jayabal, J.; Legros, B.; Ossemann, M.; Mcgrath, N.; Verrotti, A.; Tan, H. J.; Beretta, S.; Frith, R.; Iniesta, I.; Whitham, E.; Wanigasinghe, J.; Ezeala-Adikaibe, B.; Striano, P.; Rosemergy, I.; Walker, E. B.; Alkhidze, M.; Rodriguez-Leyva, I.; Ramirez Gonzalez, J. A.; D'Souza, W. J.; Calle, A.; Palacios, C.; Cairns, A.; Carney, P.; Craig, D.; Gill, D.; Gupta, S.; Lander, C.; Laue-Gizzi, H.; Hitchens, N.; Kiley, M.; Lawn, N.; Reyneke, E.; Riney, K.; Tan, M.; Tan, M.; Thieban, M.; Wong, C.; van Rijckevorsel, G.; Ferrari Strang, A. G.; Gifoni, A.; Helio, L.; Monnerat, B.; Brna, P.; Donner, E.; Jacques, S.; Jette, N.; Mclachlan, R.; Mohamed, I.; Tran, T. P. Y.; Bo, X.; Fan, S.; Guang, Y.; Li, M.; Wang, K.; Zhang, S.; Ladino, L.; Christensen, J.; Kӧlmel, M. S.; Nikanorova, M.; Uusitalo, A.; Vieira, P.; Auvin, S.; Ediberidze, T.; Gogatishvili, N.; Jishkariani, T.; Dennig, D.; Grimmer, A.; Michaelis, R.; Schubert-Bast, S.; Stephani, C.; Stodieck, S.; Vollbrandt, M.; Zellner, A.; Zafeiriou, D.; Fogarasi, A.; Halasz, P.; Chaurasia, R. N.; Jain, S.; Nair, R.; Passi, P.; Rajadhyaksha, S.; Sattaluri, S. J.; Shah, H.; Udani, V.; Costello, D.; Aguglia, U.; Bartocci, A.; Benna, P.; Ferlazzo, E.; Laino, D.; Spalice, A.; Zanchi, C.; Ali, A.; Lim, K. S.; Ramirez, A.; Anderson, N.; Barber, A.; Cariga, P.; Cleland, J.; Child, N.; Davis, S.; Dayal, V.; Dickson, C.; Doran, J.; Duncan, R.; Giri, P.; Herd, M.; Hutchinson, D.; Jones, B.; Kao, J.; Kilfoyle, D.; Mottershead, J.; Muir, C.; Nolan, M.; Pereira, J.; Ranta, A.; Sadani, S.; Simpson, M.; Spooner, C.; Timmings, P.; Walker, E.; Wei, D.; Willoughby, E.; Wong, E.; Wu, T.; Olusola, T.; Mahmud, H.; Mogul, Z.; Espinoza, J.; Vizarreta, J. H.; Baeta, E. M.; Teotonio, R.; Jocic-Jakubi, B.; Lukic, S.; Korosec, M.; Zgur, T.; Eguilaz, M. G.; Asztely, F.; Sithinamsuwan, P.; Anderson, J.; Auce, P.; Desurkar, A.; Hamandi, K.; Kelso, A.; Sanchez, V.; Sidra, A.; Smith, P.; Wehner, T.; Winston, G.; Andrade, E.; Bensalem-Owen, M.; Boudreau, M.; Caller, T.; Chapman, K.; Chari, G.; Davis, K.; Droker, B.; El-Hagrassy, M.; Eliashiv, D.; Eze, C.; Heck, C.; Kabir, A.; Kolesnik, D.; Lam, A.; Lopez, J.; Maamoon, T.; Cohen, J. M.; Maganti, R.; Nwankwo, C.; Park, K.; Proteasa, S.; Sandok, E.; Seinfield, S.; Toub, J.; Wirrell, E.; Arbildi, M.; Thien, T. T