Electroporation of single NG108-15 cells with carbon-fiber microelectrodes was characterized by patch-clamp recordings and fluorescence microscopy. To minimize adverse capacitive charging effects, the patch-clamp pipette was sealed on the cell at a 90(o) angle with respect to the microelectrodes where the applied potential reaches a minimum. From transmembrane current responses, we determined the electric field strengths necessary for ion-permeable pore formation and investigated the kinetics of pore opening and closing as well as pore open times. From both patch-clamp and fluorescence microscopy experiments, the threshold transmembrane potentials for dielectric breakdown of NG108-15 cells, using 1-ms rectangular waveform pulses, was approximately 250 mV. The electroporation pulse preceded pore formation, and analyte entry into the cells was dictated by concentration, and membrane resting potential driving forces. By stepwise moving a cell out of the focused field while measuring the transmembrane current response during a supramaximal pulse, we show that cells at a distance of approximately 30 microm from the focused field were not permeabilized.

Rheumatoid arthritis-associated joint pain is frequently observed independent of disease activity, suggesting unidentified pain mechanisms. We demonstrate that antibodies binding to cartilage, specific for collagen type II (CII) or cartilage oligomeric matrix protein (COMP), elicit mechanical hypersensitivity in mice, uncoupled from visual, histological and molecular indications of inflammation. Cartilage antibody-induced pain-like behavior does not depend on complement activation or joint inflammation, but instead on tissue antigen recognition and local immune complex (IC) formation. smFISH and IHC suggest that neuronal Fcgr1 and Fcgr2b mRNA are transported to peripheral ends of primary afferents. CII-ICs directly activate cultured WT but not FcRγ chain-deficient DRG neurons. In line with this observation, CII-IC does not induce mechanical hypersensitivity in FcRγ chain-deficient mice. Furthermore, injection of CII antibodies does not generate pain-like behavior in FcRγ chain-deficient mice or mice lacking activating FcγRs in neurons. In summary, this study defines functional coupling between autoantibodies and pain transmission that may facilitate the development of new disease-relevant pain therapeutics.

These preclinical data suggest that asenapine may exhibit highly potent antipsychotic activity with very low EPS liability. Its ability to increase both dopaminergic and glutamatergic activity in rat mPFC suggests that asenapine may possess an advantageous effect not only on positive symptoms in patients with schizophrenia, but also on negative and cognitive symptoms.

The alpha(2) adrenoceptor antagonist idazoxan enhances antipsychotic efficacy of classical dopamine D(2) antagonists in treatment-resistant schizophrenia. The mechanisms are not fully understood, but we have previously shown that the combination of idazoxan with the D(2/3) receptor antagonist raclopride, similarly to clozapine but not classical antipsychotic drugs, augments dopamine efflux in the prefrontal cortex, and also generates an enhanced suppression of the conditioned avoidance response. We have now investigated the effects of clozapine, raclopride, idazoxan and the combination of raclopride and idazoxan on (i) electrically evoked excitatory post-synaptic potentials and currents in pyramidal cells of the rat medial prefrontal cortex, using intracellular electrophysiological recording in vitro, (ii) the impaired cognitive function induced by the selective N-methyl-D-aspartate (NMDA) receptor antagonist MK-801, using the 8-arm radial maze test, (iii) the in-vivo D2, alpha(2A) and alpha(2C) receptor occupancies of these pharmacological treatments, using ex-vivo autoradiography. Whereas neither idazoxan nor raclopride alone had any effect, the combination exerted the same facilitation of glutamatergic transmission in rat prefrontal pyramidal neurons as clozapine, and this effect was found to be mediated by dopamine acting at D(1) receptors. Similarly to clozapine, the combination of idazoxan and raclopride also completely reversed the working-memory impairment in rats induced by MK-801. Moreover, these effects of the two treatment regimes were obtained at similar occupancies at D(2), alpha(2A) and alpha(2C) receptors respectively. Our results provide novel neurobiological and behavioural support for a pro-cognitive effect of adjunctive use of idazoxan with antipsychotic drugs that lack appreciable alpha(2) adrenoceptor-blocking properties, and define presynaptic alpha(2) adrenoceptors as major targets in antipsychotic drug development.

This paper presents a microfluidics-patch clamp platform for performing high-throughput screening and rapid characterization of weak-affinity ion channel-ligand interactions. This platform integrates a microfluidic chip consisting of multiple channels entering an open volume with standard patch clamp equipment. The microfluidic chip is placed on a motorized scanning stage and the method relies on the ability to scan rapidly, on the order of milliseconds, a patch-clamped cell across discrete zones of different solutions created in the open volume. Under ideal conditions, this method has the capacity to obtain kinetically resolved patch clamp measurements and dose-response curves of up to 10(3) ligand solutions in a single day.