For years, our ability to study pathological changes in neurological diseases has been hampered by the lack of relevant models until the recent groundbreaking work from Yamanaka's group showing that it is feasible to generate induced pluripotent stem cells (iPSCs) from human somatic cells and to redirect the fate of these iPSCs into differentiated cells. In particular, much interest has focused on the ability to differentiate human iPSCs into neuronal progenitors and functional neurons for relevance to a large number of pathologies including mental retardation and behavioral or degenerative syndromes. Current differentiation protocols are time-consuming and generate limited amounts of cells, hindering use on a large scale. We describe a feeder-free method relying on the use of a chemically defined medium that overcomes the need for embryoid body formation and neuronal rosette isolation for neuronal precursors and terminally differentiated neuron production. Four days after induction, expression of markers of the neurectoderm lineage is detectable. Between 4 and 7 days, neuronal precursors can be expanded, frozen, and thawed without loss of proliferation and differentiation capacities or further differentiated. Terminal differentiation into the different subtypes of mature neurons found in the human brain were observed. At 6–35 days after induction, cells express typical voltage-gated and ionotrophic receptors for GABA, glycine, and acetylcholine. This specific and efficient single-step strategy in a chemically defined medium allows the production of mature neurons in 20–40 days with multiple applications, especially for modeling human pathologies.

Background and Purpose: Anion‐selective Cys‐loop receptors (GABA and glycine receptors) provide the main inhibitory drive in the CNS. Both types of receptor operate via chloride‐selective ion channels, though with different kinetics, pharmacological profiles, and localization. Disequilibrium in their function leads to a variety of disorders, which are often treated with allosteric modulators. The few available GABA and glycine receptor channel blockers effectively suppress inhibitory currents in neurons, but their systemic administration is highly toxic. With the aim of developing an efficient light‐controllable modulator of GABA receptors, we constructed azobenzene‐nitrazepam (Azo‐NZ1), which is composed of a nitrazepam moiety merged to an azobenzene photoisomerizable group.Experimental Approach: The experiments were carried out on cultured cells expressing Cys‐loop receptors of known subunit composition and in brain slices using patch‐clamp. Site‐directed mutagenesis and molecular modelling approaches were applied to evaluate the mechanism of action of Azo‐NZ1.Key Results: At visible light, being in trans‐configuration, Azo‐NZ1 blocked heteromeric α1/β2/γ2 GABA_A receptors, ρ2 GABA_A (GABA_C), and α2 glycine receptors, whereas switching the compound into cis‐state by UV illumination restored the activity. Azo‐NZ1 successfully photomodulated GABAergic currents recorded from dentate gyrus neurons. We demonstrated that in trans‐configuration, Azo‐NZ1 blocks the Cl‐selective ion pore of GABA receptors interacting mainly with the 2′ level of the TM2 region.Conclusions and Implications: Azo‐NZ1 is a soluble light‐driven Cl‐channel blocker, which allows photo‐modulation of the activity induced by anion‐selective Cys‐loop receptors. Azo‐NZ1 is able to control GABAergic postsynaptic currents and provides new opportunities to study inhibitory neurotransmission using patterned illumination.

Optogenetic and photopharmacological tools to manipulate neuronal inhibition have limited efficacy and reversibility. We report the design, synthesis, and biological evaluation of Fulgazepam, a fulgimide derivative of benzodiazepine that behaves as a pure potentiator of ionotropic γ‐aminobutyric acid receptors (GABA_ARs) and displays full and reversible photoswitching in vitro and in vivo. The compound enables high‐resolution studies of GABAergic neurotransmission, and phototherapies based on localized, acute, and reversible neuroinhibition.

Glycine receptors (GlyRs) belong to the superfamily of pentameric cys-loop receptor-operated channels and are involved in numerous physiological functions, including movement, vision and pain. In search for compounds performing subunit-specific modulation of GlyRs we studied action of ginkgolic acid, an abundant Ginkgo biloba product. Using patch-clamp recordings, we analysed the effects of ginkgolic acid in concentrations from 30nM to 25µM on α1- α3 and α1/β configurations of GlyR and on GABAARs expressed in cultured CHO-K1 cells and mouse neuroblastoma (N2a) cells. Ginkgolic acid caused an increase in the amplitude of currents mediated by homomeric α1 and heteromeric α1/β GlyRs and provoked a left-shift of the concentration-dependent curves for glycine. Even at high concentrations (10-25 µM) ginkgolic acid was not able to augment ionic currents mediated by α2 and α3 GlyRs, or by GABAAR consisting of α1/β2/γ2 subunits. Mutation of three residues (T59A/A261G/A303S) in the α2 GlyR subunit to the corresponding ones from the α1 converted the action of ginkgolic acid to potentiation with a distinct decrease in EC50 for glycine, suggesting an important role for these residues in modulation by ginkgolic acid. Our results suggest that ginkgolic acid is a novel selective enhancer of α1 GlyRs