GABA (gamma-aminobutyric acid), the major inhibitory transmitter in the brain, goes through a transitory phase of excitation during development. The excitatory phase promotes neuronal growth and integration into circuits. We show here that spontaneous nicotinic cholinergic activity is responsible for terminating GABAergic excitation and initiating inhibition. It does so by changing chloride transporter levels, shifting the driving force on GABA-induced currents. The timing of the transition is critical, because the two phases of GABAergic signaling provide contrasting developmental instructions. Synergistic with nicotinic excitation, GABAergic inhibition constrains neuronal morphology and innervation. The results reveal a multitiered activity-dependent strategy controlling neuronal development.

Background:The molecular basis for sodium channel inhibition by spider venom peptides is poorly understood. Results: Key toxin residues and structural features important for activity of huwentoxin-IV are identified. Conclusion: Toxin activity involves a hydrophobic protrusion surrounded by a ring of basic residues. Significance: New structure-function information may provide a foundation for the design of peptides with therapeutic potential.

Background and Purpose An increasing body of evidence suggests that the purinergic receptor P2X, ligand‐gated ion channel, 7 (P2X7) in the CNS may play a key role in neuropsychiatry, neurodegeneration and chronic pain. In this study, we characterized JNJ‐47965567, a centrally permeable, high‐affinity, selective P2X7 antagonist. Experimental Approach We have used a combination of in vitro assays (calcium flux, radioligand binding, electrophysiology, IL‐1β release) in both recombinant and native systems. Target engagement of JNJ‐47965567 was demonstrated by ex vivo receptor binding autoradiography and in vivo blockade of Bz‐ATP induced IL‐1β release in the rat brain. Finally, the efficacy of JNJ‐47965567 was tested in standard models of depression, mania and neuropathic pain. Key Results JNJ‐47965567 is potent high affinity (pKi 7.9 ± 0.07), selective human P2X7 antagonist, with no significant observed speciation. In native systems, the potency of the compound to attenuate IL‐1β release was 6.7 ± 0.07 (human blood), 7.5 ± 0.07 (human monocytes) and 7.1 ± 0.1 (rat microglia). JNJ‐47965567 exhibited target engagement in rat brain, with a brain EC50 of 78 ± 19 ng·mL−1 (P2X7 receptor autoradiography) and functional block of Bz‐ATP induced IL‐1β release. JNJ‐47965567 (30 mg·kg−1) attenuated amphetamine‐induced hyperactivity and exhibited modest, yet significant efficacy in the rat model of neuropathic pain. No efficacy was observed in forced swim test. Conclusion and Implications JNJ‐47965567 is centrally permeable, high affinity P2X7 antagonist that can be used to probe the role of central P2X7 in rodent models of CNS pathophysiology.

Pain places a devastating burden on patients and society and current pain therapeutics exhibit limitations in efficacy, unwanted side effects and the potential for drug abuse and diversion. Although genetic evidence has clearly demonstrated that the voltage-gated sodium channel, Nav1.7, is critical to pain sensation in mammals, pharmacological inhibitors of Nav1.7 have not yet fully recapitulated the dramatic analgesia observed in Nav1.7-null subjects. Using the tarantula venom-peptide ProTX-II as a scaffold, we engineered a library of over 1500 venom-derived peptides and identified JNJ63955918 as a potent, highly selective, closed-state Nav1.7 blocking peptide. Here we show that JNJ63955918 induces a pharmacological insensitivity to pain that closely recapitulates key features of the Nav1.7-null phenotype seen in mice and humans. Our findings demonstrate that a high degree of selectivity, coupled with a closed-state dependent mechanism of action is required for strong efficacy and indicate that peptides such as JNJ63955918 and other suitably optimized Nav1.7 inhibitors may represent viable non-opioid alternatives for the pharmacological treatment of severe pain.