Mapping cortical mesoscopic networks of single spiking cortical or sub-cortical neurons.

Understanding the basis of brain function requires knowledge of cortical operations over wide-spatial scales, but also within the context of single neurons. In vivo, wide-field GCaMP imaging and sub-cortical/cortical cellular electrophysiology were used in mice to investigate relationships between spontaneous single neuron spiking and mesoscopic cortical activity. We make use of a rich set of cortical activity motifs that are present in spontaneous activity in anesthetized and awake animals. A mesoscale spike-triggered averaging procedure allowed the identification of motifs that are preferentially linked to individual spiking neurons by employing genetically targeted indicators of neuronal activity. Thalamic neurons predicted and reported specific cycles of wide-scale cortical inhibition/excitation. In contrast, spike-triggered maps derived from single cortical neurons yielded spatio-temporal maps expected for regional cortical consensus function. This approach can define network relationships between any point source of neuronal spiking and mesoscale cortical maps.

A small-molecule screen in C. elegans yields a new calcium channel antagonist.

Small-molecule inhibitors of protein function are powerful tools for biological analysis and can lead to the development of new drugs. However, a major bottleneck in generating useful small-molecule tools is target identification. Here we show that Caenorhabditis elegans can provide a platform for both the discovery of new bioactive compounds and target identification. We screened 14,100 small molecules for bioactivity in wild-type worms and identified 308 compounds that induce a variety of phenotypes. One compound that we named nemadipine-A induces marked defects in morphology and egg-laying. Nemadipine-A resembles a class of widely prescribed anti-hypertension drugs called the 1,4-dihydropyridines (DHPs) that antagonize the alpha1-subunit of L-type calcium channels. Through a genetic suppressor screen, we identified egl-19 as the sole candidate target of nemadipine-A, a conclusion that is supported by several additional lines of evidence. egl-19 encodes the only L-type calcium channel alpha1-subunit in the C. elegans genome. We show that nemadipine-A can also antagonize vertebrate L-type calcium channels, demonstrating that worms and vertebrates share the orthologous protein target. Conversely, FDA-approved DHPs fail to elicit robust phenotypes, making nemadipine-A a unique tool to screen for genetic interactions with this important class of drugs. Finally, we demonstrate the utility of nemadipine-A by using it to reveal redundancy among three calcium channels in the egg-laying circuit. Our study demonstrates that C. elegans enables rapid identification of new small-molecule tools and their targets.